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Description
Holley HP EFI ECU and Harness Kits 550-604MPFI HP ECU AND HARNESS KIT Looking for a plug and play alternative for your stock or built late model factory EFI engine? How about a replacement ECU for your older Holley C950? Holley has you covered. HP EFI ECU and harness kits are designed to be used with popular factory EFI engines as an alternative to the factory ECU and harness or as a replacement for your C950 ECU. The HP allows you to accurately control the fuel and ignition of your engine
MPFI HP ECU AND HARNESS KIT
Looking for a plug and play alternative for your stock or built late model factory EFI engine? How about a replacement ECU for your older Holley C950? Holley has you covered. HP EFI ECU and harness kits are designed to be used with popular factory EFI engines as an alternative to the factory ECU and harness or as a replacement for your C950 ECU. The HP allows you to accurately control the fuel and ignition of your engine along with additional controls for nitrous, boost or water meth.
Features:
- Optional 5.7” full-color touchscreen LCD allows easy on-the-fly tuning, data-logging or can be used as an easy to see graphical gauge panel
- Eight sequentially driven 8:2 peak and hold injector drivers, capable of driving up to 16 low or high impedance injectors as a standard feature. Multiple staged injector strategies
- Eight channel Distributorless Ignition (DIS)outputs capable of directly driving “Smart” ignition coils or Holley DIS coils. Will drive 2 wire coils with the addition of PN 554-112 high current coil driver module
- Integrated single channel wide band oxygen sensor control. Works with NTK or Bosch sensors
- Internal data-logging standard with a huge 2GB of memory
- 4 Stage progressive nitrous control
- Turbo boost control
- Integrated water/methanol injection control
- Self-tuning fuel table strategy greatly simplifies tuning process
- Individual cylinder fuel and spark control allows you to unlock your engine’s potential
- Works with 4, 6, 8 cylinder engines
- Unique lb/hr based fueling strategy greatly simplifies and commonizes tuning
- Advanced idle, closed loop, and enrichment strategies allow for very stable operation
- ECU is fully potted and can be mounted in the engine compartment or interior
- Sealed automotive and marine grade connectors
- Allows for use of common OEM sensors as well as customer sensor calibration input
- Ignition Plug and Play with GM HEI, Ford TFI, magnetic and hall effect trigger, and other ignition systems. New Plug and Play applications in process. Custom settings can be configured to allow many other applications
- 1-5 Bar MAP sensor capability
- Two channel knock control sensor Inputs for both one or two wire knock sensors
- Dedicated fuel and oil pressure inputs
- Controls both stepper and PWM Idle Air Control (IAC) motors
- Speed density, Alpha-N, or combination fueling strategies
- 4 Programmable high or low Pulse Width Modulated (PWM) outputs and 4 fully configurable inputs can be configured for use
- 4 Stage nitrous oxide control
- Fully featured nitrous control eliminates the need for a separate nitrous controller device
- Can be configured “Wet” or “Dry” with closed loop feedback
- Progressive control based on time, RPM, or boost, requires part # 554-111
- Lean or rich safety cutoff
- Full timing retard/control configurability per stage based on RPM or time
- Integrated Water/Methanol injection control
- Uses Holley Water/Meth solenoids specially designed and calibrated for use with this EFI system to allow the user to enter Water/Meth flow as a percentage of fuel injector flow for Water/Meth tuning precision unmatched in the industry
Application
-
Universal
Specs
| Brand | Holley EFI |
|---|---|
| Emission Code | 3 |
| Ignition Type | Coil - (No Timing Control) |
| Ford TFI | |
| GM HEI Small Cap | |
| Holley Dual Sync Distributor | |
| Injector Connector | Jetronic / Minitimer (Bosch) |
| Product Type | HP EFI Kit |
| Part Number | 550-604 |
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4.7 ★★★★★
Based on 23 reviews
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Product Reviews
★★★★★ 5
NOT JUST FOR EASTER
Format: Paperback, Format: Paperback
I ordered this book firstly because it talks about the Bible. It's meant for someone who wants to read something meaningful in the weeks leading up to Easter. It’s a thoughtful, well-written devotional that can help you to reflect on the word of God and the significance of Christ’s death and resurrection.
The best thing about this book is that it’s designed as a 30-day reading plan, and that makes it easy to incorporate into your daily routine. Each day’s reading is only about one and 3/4 of a page - short enough to fit into a busy schedule, but each devotional is still meaningful. I think it's designed like that so you can do a quick reading, like inthe morning when you get up and have your morning tea, or when you're in bed at night. It also gives you something to reflect on throughout the day.
The devotionals don't just focus on Easter, it's based on passages throughout the Bible. It shows you how scriptures ultimately lead to the resurrection of Jesus Christ. All the way from Genesis to Revelation, it defines how God's plan of redemption through the cross has been laid out for years, long before Jesus's birth (and after his death and resurrection). Each devotional has reflection questions to make you think about what you read, along with a prayer.
This would be the perfect book for someone who wants to get into reading the Bible but doesn't know where to start. It has a lot of Biblical insight and depth. Its simple but powerful and emotionally moving. It would literally take you about 5-7 minutes of your day to read each devotional, and it gives you something to reflect on the rest of the day.
The thing about it is that it isn't just for Easter; this can be read any time someone wants a Christ-centered devotional to lift their spirits or to learn more about the Bible. I would definitely buy this again for a gift, and will be looking into other devotionals by this author. I’m very happy with this book and would definitely give it five stars, and if you are questioning your faith - Christ died for you, all you have to do is ask for clarity, and He will provide.
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Reviewed in the United States on March 11, 2026
★★★★★ 5
Excellent Easter Devotional
Format: Paperback
This thirty-day Easter Devotional is just as edifying as any writing from Paul David Tripp. Each day offers opportunity for context, reflection, application, and prayer, ever pointing more to the hope of the resurrection as the day draws near. This would be an excellent devotional to lead one's family through or to read as an individual. The book is well constructed as far as paper back goes, and a wonderful value for the quality of content. It's printing is clearly legible and well centered on each page for easy readability, and the book is comfortable to hold. The hope of the gospel shines brilliantly in this short seasonal devotional. My understanding of how old testament passages point to the fulfillment of Christ has been deepened, thus broadening my understanding of the text in daily Bible study. I highly recommend this particular book, as well as many others from this author! May it build every reader up in the full knowledge of God which bears much good fruit in love and good deeds, as we not only rejoice in what has been accomplished already, but also look forward to what God has to come upon the Savior and Judge's return. May all glory, honor, blessing and praise be to Him who has conquered the grave on behalf of the redeemed.
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Reviewed in the United States on March 23, 2026
★★★★★ 5
Excellent devotion book for any seasons
Format: Paperback
Didn't expect much when I ordered this devotional.
After starting the first day, I realize this is an excellent devotional not just for Easter.
Content:
It covers the whole bible from Genesis all the way to Revolution. Of course, it doesn't cover every single book or every single detail in the bible. But rather than just talking about Jesus in the four gospels to His resurrection, it starts from the very beginning (Genesis) and talks about how sins entered the world and why Jesus came to Earth to save us from sin all the way to the completion of the salvation plan (Revelations). It gives a much better scope then just focusing on the events in Easter alone.
Length of each devotion:
There are 30 days of devotions. Each day is only a 2 page read which is good for people who just started or trying to get back to the habit of daily devotions. It doesn't take much time so it's less intimidating and there is no excuse not to do it.
The structure of each devotion:
There is the main bible passage, a personal sharing/message from the author as well as a biblical teaching based on the passage of the day. There there is a short reflection section and a sample prayer leading us to respond. The structure is well laid out for a concise but meaning devotion.
The passage and the sharing in each day is very insightful and though provoking.
Overall, this is a great devotional that I highly recommended.
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Reviewed in the United States on February 20, 2026
★★★★★ 4
Thoughtful Easter devotional, though the writing style may not resonate with everyone
Format: Paperback, Format: Paperback
As Easter approaches, I was interested in spending some time with this devotional. One thing I appreciated right away is how Paul David Tripp connects passages from across the Bible to the deeper meaning of Easter. The devotional begins with references in the Old Testament and traces the thread of prophecy forward toward the ultimate sacrifice and resurrection. That connection between early scripture and the events of Easter is an important foundation of the Christian story, and the book highlights it well.
What I liked:
Carefully selected Bible passages that connect Old Testament prophecy with the Easter story
A devotional structure that encourages reflection throughout the season
An accessible way to revisit the narrative from prophecy to resurrection
Where it didn’t fully connect for me:
The author’s narrative style may be a matter of personal preference. His writing is often elegant and reflective, but at times it felt somewhat fragmented or incomplete to me. I personally tend to connect more with a slightly more straightforward, conversational style of devotional writing.
That said, this doesn’t mean the book lacks value. Readers who appreciate a more poetic or contemplative tone may find it quite meaningful.
Overall:
Even though the writing style wasn’t a perfect fit for me, this is still a worthwhile Easter devotional. It provides a thoughtful way to reflect on the journey from prophecy to resurrection and would make a good companion for the Easter season.
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Reviewed in the United States on March 8, 2026
★★★★★ 5
Equally deep and approachable devotional
Format: Paperback
This really is an everyday devotional in that it is rich and engaging whether going through it for the Lenten season or any other time of the year. It focuses on the Gospel message from our sin and need for a Savior, through the Lord’s redemptive plan and faithful fulfillment through Jesus. Each daily entry is just two pages, but has a balance of depth and approachability that makes it feel full and spiritually satisfying. The author’s personal stories and way of framing the biblical passages is relatable, and I was immediately drawn into it. I especially like how the devotional begins with the Old Testament scriptures, revealing themes and prophetic pictures that I hadn’t seen before, and then gradually works into the New Testament, even through Revelation! If going through this during Lent, the topics build up the anticipation for Resurrection Sunday and are arranged very meaningfully. The reflection questions are also really good at bringing out deep reflections and a personal response to the biblical passage and thematic focus of the devotional. I’ve made it through most of the devotional at this point, and am thoroughly enjoying it. Highly recommend!
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Reviewed in the United States on March 16, 2026
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