Shipping Estimate
USA
- USA
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- USA
- CAN
Ships within 48 hours · Estimated delivery Jul 13 - Jul 18
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
4.8 ★★★★★
Based on 298 reviews
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Product Reviews
★★★★★ 5
Nice little jewelry box
Color: Cloud White, Material Type: Paper, PU
Just what I wanted in size and available compartments. The only thing I am hesitant about is the paper outside. Mine is white and may get dirty quickly.
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on March 16, 2026
★★★★★ 5
A Lovely and Useful Gift
Color: Cloud White, Material Type: Paper, PU
I bought this SONGMICS jewelry organizer box as a gift and it was a great choice. The design is beautiful and it keeps jewelry well organized. It’s compact and perfect for travel or everyday use. The person I gave it to loved it and uses it all the time.
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Reviewed in the United States on March 8, 2026
★★★★★ 5
Small and cute!
Color: Cloud White, Material Type: Paper, PU
Its perfect!
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Reviewed in the United States on May 25, 2026
★★★★★ 5
So cutie
Color: Cloud White, Material Type: Paper, PU
This is a bit large for a travel size jewelry box lol I really thought it was going to be a bit smaller than what it was. I can see why some of the ladies in the comments are saying they’re using it as their main jewelry box since they don’t have much jewelry for a standard sized jewelry box.
With that being said, it’s cute and CAN be small enough for travel. It fits a lot and I got this one in particular bc I like that it has a bigger lower compartment for larger pieces. It’s a nice quality travel jewelry box. It’ll fit my needs. But if you have a knack for packing small and you value space. I’d say skip on this one or do due diligence to double check the measurements to see if it’s something you’re okay with packing.
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Reviewed in the United States on January 31, 2026
★★★★★ 5
Good value
Color: Jelly Pink, Material Type: Paper, PU
This is a great jewelry box for travel or to just keep at home. Very stylish and holds more than it looks like it would.
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Reviewed in the United States on February 10, 2026