Shipping Estimate
USA
- USA
- CAN
- USA
- CAN
Ships within 48 hours · Estimated delivery Jul 14 - Jul 19
For Your Every Summer RSVP, with Code: SUMMER15
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:
- 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
4.4 ★★★★★
Based on 1822 reviews
Sort
Product Reviews
★★★★★ 1
Will continue to be a customer
Color: Deep Gray, Size: 10
Dress pants did not fit right on my grandson. Too big in the waist and wasn't long enough. I returned the pants.
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on April 9, 2026
★★★★★ 5
Smart-Looking Pants That Fit Well
Color: Navy Blue, Size: 8
I had my son wear these for a church, and they looked sharp without being too stiff. The adjustable waist makes them comfortable, and the fabric feels durable enough to handle a few hours of running around. They held their shape well and didn’t wrinkle too easily.
After a couple of wears, they still look crisp and clean. The overall fit and finish make them feel like a well-made pair of dress pants.
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on April 2, 2026
★★★★★ 5
Great Fit
Color: Royal Blue, Size: 10
Cute vest perfect for my 10 yr old
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on May 19, 2026
★★★★★ 5
Kids Formal Vest Review
Color: Royal Blue, Size: 12, Color: Royal Blue, Size: 12
At the time of review, the price was $17.09. It seems to be correctly priced for the value it provides.
I found this vest to be versatile, suitable for a range of formal and semi-formal occasions, from weddings to school events, and capable of being dressed up or down. The fit generally seemed accurate or slightly generous, though it does come with the adjustable back strap offering some customization. The overall quality of the vest, including its construction and stitching, appeared to be good, with a durable and well-made feel. It presented a polished and sharp appearance that could elevate an outfit, and the color is very close to the product image. The material felt substantial and structured, yet breathable, often featuring a silky lining and a notable texture and seems to be machine washable. Based on the quality I've seen, I considered this vest to offer good value for its price point.
The vest provides a functional option for children's formal wear. Its design and construction suggest practical utility for various events... or your kid can just wear it all the time like mine does.
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on March 30, 2026
★★★★★ 5
Great Boys Suit Vest
Color: Black, Size: 12, Color: Black, Size: 12
I recently had a chance to pick up this boy's suit vest for my upcoming wedding, and it is absolutely perfect. It fits my son so well, running very true to size. The material is so silky smooth and soft, he absolutely loves it. He's autistic and has a thing about different fabrics and this does not irritate or bother him at all. It is going to be perfect over his long sleeve button down shirt. The best looks amazing on him, and the black color is definitely a very dark true black. It is such a great value for the money, you will not be disappointed! I highly recommend picking this up if you need one for your boy or if you have a family member who needs one for an upcoming event.
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on April 4, 2026
recommand products
Stocker Hill
24.00
BEASTMODE/MAMMAS COOKING VOL 2: Small town BIGG taste “DA BORO 07843” HOPATCONG NJ
24.00
Vectors of Freedom in World Diplomacy: Diplomacy Is the Art of the Possible and Not the Science of the Desperate
17.00
Lateral Hazard
18.00
A Pensive Peregrination: Vignettes of a Spiritual Traveler
23.00