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- USA
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Ships within 48 hours · Estimated delivery Jul 13 - Jul 18
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Description
HP EFI ECU & Harness Kits - 550-601Overview: 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
Overview:
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:
NEW V2 SOFTWARE FEATURES - “Quick Start” ignition and fueling strategy for LS x Engines
- Data Logger. Scalable axes, Smoothing, Multiple graph view ability, Pre-defined notes fields and many more
- Strip Chart Real-Time Data Viewer
- Integrated Boost Control - Boost vs Time, Boost vs Gear (Time or RPM), Boost vs RPM, Boost vs Speed, Launch control. Boost launch builder, Over-boost safeties, Boost scramble
- Traction Control - Power reduction via timing, nitrous percentage or boost (Requires Davis Technologies Holley Module)
- “Quick Start” fueling for all engines
- Option for VE based fueling strategy
- Fuel Map and Learn Function Smoothing
- Configurable User Password Protection
- Fully Configurable lap top Gauge Panel
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
- Plug and Play control of factory GM 24x and 58x LSx engines
- 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 24x and 58x LSx engines, 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:
| Year | Make | Model | Submodel | Engine Size |
|---|---|---|---|---|
| Universal |
Specs:
| Brand | Holley EFI |
|---|---|
| Emission Code | 3 |
| Ignition Type | Coil - (No Timing Control) |
| Ignition Type | GM HEI Small Cap |
| Ignition Type | Holley Dual Sync Distributor |
| Injector Connector | Jetronic / Minitimer (Bosch) |
| Product Type | HP EFI Kit |
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
4.3 ★★★★★
Based on 1263 reviews
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Product Reviews
★★★★★ 3
Fabric way to heavy.
Fit Type: Regular, Size: Medium, Color: White
Cute, but material is WAY to heavy, like the heaviest duty denim I've ever seen. Wanted this to be a cute coverup. If you're needing something while breaking broncos or riding your motorcycle would probably be great. I kept it for a while because it was good quality and well made, but it ended up in the donation pile as I'd never wear this.
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on June 10, 2026
★★★★★ 5
Awesome jacket
Fit Type: Regular, Size: Medium, Color: Stone Dark Wash
Love it so not too long or too short but just right and the color is out of sight and fits awesome
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on June 12, 2026
★★★★★ 5
Old school denim — not stretchy
Fit Type: Regular, Size: X-Small, Color: Authentic Medium Wash
Fabric used is old school denim — not the thin, stretchy stuff that pretty much everything called “denim” is today. It is 99% cotton (20% of which is recycled cotton) and 1% elastane, but I can’t feel any stretch in the fabric. It is a substantial, non-stretchy denim that gives the jacket really good structure. It has a higher end fit and look than the price would suggest.
I wanted a more fitted denim jacket so ordered an XS even though according to the size chart I need a small. (I have a 34.5” bust, 28” waist at 118 pounds 5’4”.) It still buttons over a t shirt or lightweight sweater with freedom for movement/without being tight, but if I wanted a roomy fit or the ability to wear a heavier sweater or sweatshirt underneath and still be able to comfortably button it I would have needed a small. The shoulders are cut broad — I have very broad shoulders and the XS surprisingly fits my shoulders well. This jacket may not be the greatest fit for you if you have very narrow shoulders, unless you are going for an oversized look.
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Reviewed in the United States on May 17, 2026
★★★★★ 5
made well
Fit Type: Regular, Size: Large, Color: Iced Light Wash
I couldn't get this in my size (medium) so I ordered large. it's a little large in the shoulders, but it still looks good. it is a well made, substantial jacket. I love it!
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Reviewed in the United States on June 12, 2026
★★★★★ 5
good stretch
Size: 10 Long, Color: Dark Wash
Honestly, these are one of those surprisingly good basics—especially for the price.
The biggest standout is the stretch. They’re really comfortable and move with you, so they don’t have that stiff “jeans” feeling. They hug your body in a flattering way without feeling too tight or restrictive, which makes them easy to wear all day.
The mid-rise fit is also a sweet spot—not too low, not too high—so they’re super versatile with different tops.
What I liked:
Very stretchy and comfortable (almost feels like jeggings, but still looks like denim)
Flattering skinny fit through the legs
Easy everyday jeans—work, errands, going out
Great value for the price
What to know:
Material is on the thinner side (more comfort than “structured denim”)
They can lose shape slightly after a full day of wear
Not the most durable long-term compared to higher-end denim
Final thoughts:
These are perfect if you want cute, comfortable, affordable jeans you can throw on with anything. Not premium denim, but for everyday wear—they definitely get the job done and are worth having in your rotation.
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on April 10, 2026
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