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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:
- 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
4.6 ★★★★★
Based on 20 reviews
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Product Reviews
★★★★★ 5
Very nice valet tray that gives a dresser or nightstand a much nicer look, and keeps EDC organized.
We’ve been using this sandalwood valet tray (with black "leather" inserts) for about five days, and it has quickly become a favorite for keeping the dresser top organized. It sits neatly on our tallboy dresser, staying put without any sliding, which is a big plus. The tray’s size is just right. This tray is not too bulky, but spacious enough to hold keys, watch, phone, etc., basically all the stuff carried in pockets daily.
The wood has a smooth, polished feel, and the stain has a beautiful color which gives it a rich, elegant look that elevates the whole setup. What stands out most are the soft, leather-like inserts lining the compartments. They add a touch of luxury and keep items like my watch from getting scratched or sliding around with a slight bump. I also appreciate the thoughtful design of the notches cut out for phone charging cables. Having those notches makes it easy to keep a phone powered up without a mess of cords.
This valet tray feels well-crafted and sturdy, though I would not mind it if the compartments were a tad deeper for bulkier items like a wallet. It’s practical and looks far more refined than the plastic trays I’ve used before, and I feel it gives an excellent value for the money, given today's pricing (July 20, 2025). For anyone looking to tidy up their space with something that feels upscale yet functional, this tray is worth a look.
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Reviewed in the United States on July 20, 2025
★★★★★ 5
5 ⭐️⭐️⭐️⭐️⭐️ STARS! Great valet tray for keys and wallets
This valet tray is very classy and made a beautiful wood with nice little touches all around in terms of design. I really like this on my side table in our foyer, and we place our keys, wallets and odd knickknacks that we bring in from time to time. This makes it very easy so not forget or replace things if we have a designated area like this valet pad. This gets my "TRIED-and-TRUE" SOLID 5 ⭐️⭐️⭐️⭐️⭐️ STARS Rating!
I only give five star ratings to items that I use and exceed my expectations for quality, functionality, ease-of-use, premium appearance/looks, durability, & when possible: Sustainability/Ease on the Environment. I hope my review helped you gain some insight and I appreciate you taking the time to read it. Thank you!
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Reviewed in the United States on July 29, 2025
★★★★★ 5
Extremely helpful keeping remotes in order
Color: Blue, Size: Small
Nice quality remote control holder, makes it easy to find what you need, organized life is an easier life to live ! Great price too and it looks good ! This was a great little buy, I brought one for my Mom and another for the guest bedroom.
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Reviewed in the United States on December 18, 2025
★★★★★ 5
Never lose a remote again
Color: Black, Size: Large, Color: Black, Size: Large
Perfect for our kitchen table!!
Bigger and nicer than expected. Holds several remotes. Nice have remotes all in one place in kitchen where tv is
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Reviewed in the United States on February 28, 2026
★★★★★ 5
Very Handy!
Color: Gray, Size: Large
I love this remote holder! It is large enough to hold several remotes, cell phone, glasses and other frequently used items.
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Reviewed in the United States on April 15, 2026