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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
4.5 ★★★★★
Based on 30 reviews
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Product Reviews
★★★★★ 3
Protection with days of white residue
Style: SPF 50 Roll On, Size: 3 Fl Oz (Pack of 1)
Mineral sunscreens have yet to master blending in and this is no different. If you're thinking of hitting the beach with your sexy bum protected it'd better be a ghost beach because you'll look like you've been dipped in white paint. Oh, and it doesn't wash off, so be prepared to look like Casper for days to come.
It rolls on fine if you shake it well first and it does protect.
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Reviewed in the United States on June 8, 2025
★★★★★ 5
Neutrogena clear face loción de protección para el sol
Size: 3 Fl Oz (Pack of 1), Style: SPF 50
Neutrogena Clear Face Sun Protection Lotion is one of the most popular options for the face, especially if you have oily or acne-prone skin.
General opinion: it is a very good sunscreen for daily use, light and designed not to cause outbreaks.
The positive:
* It is oil-free and non-comedogenic, that is, it does not usually cover pores
* It has a light texture and "matte" type, it does not leave the skin greasy
* Absorbs quickly and can be used under makeup
* Offers good SPF 50 protection against UVA/UVB rays
* Many people with acne skin say that it does not cause pimples
The not so good:
* On very oily skin it can be a little shiny over the hours
* It is not super moisturizing (if you have dry skin, it may feel a little "light")
* Some people may be slightly irritated if they have very sensitive skin
Final opinion:
It is a highly recommended sunscreen if you have combination or oily skin and want something that does not cause acne. It is practical, cheap and reliable for day to day, but it is not the most "perfect" if you are looking for a totally dry finish or super hydration.
If you want, tell me your skin type (dry, oily or mixed) and I'll tell you if it's the best option for you or if there's an even better one.
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Reviewed in the United States on May 16, 2026
★★★★★ 5
Matte, weightless, mildly drying
Size: 3 Fl Oz (Pack of 1), Style: SPF 50, Size: 3 Fl Oz (Pack of 1), Style: SPF 50
Very good sunscreen. It is very similar to the Neutrogena Ultra Sheer sunscreen but with less/minimal fragrance. It absorbs immediately and feels matte and invisible. The only slight downside is that the silica in the sunscreen is actually so good at absorbing oil that it is mildly drying. This is great for people with oily skin, but people with acne like myself often use retinoids that are already very drying, and this can magnify the dryness. I often follow this sunscreen with some moisturizer to counteract the drying effect.
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Reviewed in the United States on May 2, 2026
★★★★★ 5
No white cast.
Size: 3 Fl Oz (Pack of 1), Style: SPF 50
Doesn't leave a white cast on your face as long as you rub it in enough. It also doesn't break me out. Good product.
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on May 14, 2026
★★★★★ 5
Great - effective sunscreen that isn't oily
Size: 3 Fl Oz (Pack of 1), Style: SPF 50
Works well, doesn't make your skin oily, almost disappears when you put it on. Made for faces but of course works anywhere else as well.
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on May 8, 2026