SKU: 5270546285

Holley HP EFI ECU and Harness Kits 550-604

Sale price$1237.47 Regular price$1374.97
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  • CAN

Ships within 48 hours · Estimated delivery Oct 10 - Oct 15

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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
Shipping Notes
  • Free Standard Shipping on $100+ Orders to the USA.
  • Except Preorder products are shipped in 48 hours.
  • Delivery to the USA:
  1. Standard Shipping : 3-10 business days
  • If time is of the essence, please consider selecting expedited delivery for faster service.
Exchange/Return Notes
  • We offer a 30-day return/exchange service after receiving.
  • Final sale items are not eligible for returns or exchanges.
  • To process your return/exchange, please contact us at [email protected]
  • Please click here for more details>>> Return & Exchange Policy
SKU: 5270546285

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4.1 ★★★★★
Based on 12 reviews
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Verified Purchase
POPSCHERRI
Battle Creek, US
★★★★★ 3
Not the best for REAL CHEWERS.
Color: Blue
My dogs love to chew and these didn’t last too long. It did keep them busy and I probably will buy these again but don’t expect much resistance of yours have big dogs that love to chew toys.
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on June 6, 2026
J
Verified Purchase
jennifer Millage
Waukegan, US
★★★★★ 5
Extremely hard and durable
Color: Blue
These are very hard , but my puppy lives them and my large dog can't tear them up, so that is a huge plus.
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on April 8, 2026
J
Verified Purchase
Jazzlyn McClure
Battle Creek, US
★★★★★ 5
Large breed approved
Color: Blue
these incredible aggressive chew toys – they've seriously been a game-changer for my pups! I know it's a bit late, but better late than never, right? I've got a couple of power chewers at home, a Rottweiler and a Labrador, and anyone with big dogs knows the struggle of finding toys that actually last. These bad boys have been in constant rotation for over a year now, and I'm genuinely impressed by their resilience. They're incredibly tough! Funnily enough, we originally had three, but now we're down to just one. The others aren't broken, though – I'm pretty sure my dogs just loved them so much they've hidden them away in some secret stash, as they tend to do with their favorite treasures! Beyond just being durable, these toys have been a massive help with their training. They’re fantastic for redirecting all that enthusiastic chewing away from my furniture and shoes, which, let's be honest, is a huge win for any pet parent! Considering how long they've held up to some serious chomping, the price point is absolutely spot on. You definitely get great value for your money.watch your toe they are heavy. If you've got a dog that's a champion chewer, you absolutely need to try these out. They're a lifesaver!
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on May 21, 2026
C
Verified Purchase
Christine Petrowsky
Boise, US
★★★★★ 5
Great all around
Color: Blue
We have 4 dogs, lab, pit bull, golden retriever, great dane, I bought 4 sets, they are constantly played and chewed on, and are still around everywhere, great to chew on and play with
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on May 27, 2026
J
Verified Purchase
Jan Keene
Carnegie, US
★★★★★ 5
Durable chew toy.
Color: Blue
My dog loves these. She chews on them a lot. She seems to like the different shapes. She is part Pit and an aggressive chewer. These chew toys last a long time. And I love the three pack so if we lose one, we always have a spare.
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on May 27, 2026

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