Pay in installments of $374.99 with
,
and
Shipping Estimate
USA
- USA
- CAN
- USA
- CAN
Ships within 48 hours · Estimated delivery Sep 20 - Sep 25
For Your Every Summer RSVP, with Code: SUMMER15
Description
Holley HP EFI ECU and Harness Kits 550-606NHP ECU AND HARNESS, FORD MPFI, NTK Looking for a alternative for your stock or built late model factory FORD 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
HP ECU AND HARNESS, FORD MPFI, NTKLooking for a alternative for your stock or built late model factory FORD 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
- 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
- Includes NTK wideband oxygen sensor
Application
- Universal
Specs
| Brand | Holley EFI |
|---|---|
| Emission Code | 3 |
| Ignition Type | Coil - (No Timing Control) |
| Ford TFI | |
| Holley Dual Sync Distributor | |
| Injector Connector | Jetronic / Minitimer (Bosch) |
| Product Type | HP EFI Kit |
| Part Number | 550-606N |
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 29 reviews
Sort
Product Reviews
★★★★★ 3
Effective, but gave me a headache
Size: 30 Count (Pack of 1)
I did and do like these. I find it takes the edge off my anxiety. Oddly enough, they give me a headache the next morning.
I tried only taking one pill at bedtime (instead of a second one halfway through the night); I made sure it wasn’t dehydration; I took electrolyte solution with it. I’ve pretty much eliminated anything else that a headache could’ve been caused by that I can think of.
They work well enough for me that on some nights it’s going to be toss up and I will still take it. But it’s kind of a drag knowing that something natural that works has a residual headache the next morning.
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on August 1, 2025
★★★★★ 5
Day 1 and A Week ish Later
Size: 30 Count (Pack of 1)
I was taking Olly Stress Relief gummies for a while to control anxiety, hyperactivity and racing thoughts, and they worked great. Recently I noticed that they were becoming a lot less effective and started searching for alternatives. This was my first choice and I've only used it this morning. Took one pill. So far I have noticed a lighter mood, lack of racing thoughts, and an overall feeling of being slowed down. I can focus on conversations better, and it slightly enhanced my ability to taste, flavors seem more vibrant.. I am a bit more "lazy feeling" as others mentioned, and I did get the lavender burps. They're not horribly obnoxious for me, just a bit different. Burps lasted maybe half an hour. So far I like it.
Edit: it's been over a week now. The first few days I dealt with random headaches on and off, but did get benefits as stated above. After my body adjusted I stopped having the headaches and the "lazy" feeling. The lavender burps are still a thing and so is short term lavender breath right after taking a pill. You can describe it like a light lingering, kinda like toothpaste has a minty aftertaste, but lavender instead. For the most part I would still say it helps. It does not hit as hard as the first few days, but it is helping somewhat.
Benefits for me: Less overstimulation in public, better ability to relax after work, anxiety is more "inconvenience", easier to focus, deeper sleep, less irritability.
Cons for me: Short term lavender breath, vivid and unusual dreams, 2-3 day initial adjustment period for unpleasant side effects.
What I'm doing: Taking one pill around 7-7:30pm daily with lots of water. Taking late to sleep off any potential unpleasant initial effects, and get better sleep.
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on August 31, 2024
★★★★★ 4
Finally, a Calm That Feela Natural
Size: 90 Count (Pack of 1)
I've tried a lot of "calm" supplements over the years, and Nature's Way Calm Aid is one of the few I've actuallt reordered.
I started taking it during a stressful stretch at work when my mind wouldn't slow down at night. Very shortly after taking it I felt more settled and less on edge. it takes the edge off without making me feel like I'm dragging through the day.
The softgels are small and easy to swallow with no weird aftertaste. This has been a real game changer for me.
If you're looking for something subtle but effective to help you stay calm and focused, CalAid is definitely worth trying.
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on February 16, 2026
★★★★★ 5
Great Addition to My Daily Routine
Size: 16 Ounce (Pack of 1)
Excellent Quality MCT Oil — Great Addition to My Daily Routine
I purchased this MCT Oil and have been very pleased with it. It is light, smooth, and easy to add to my daily routine without changing the taste of my food or drinks. I especially like that it mixes well in coffee, tea, smoothies, and even oatmeal. It does not have a strong flavor or unpleasant aftertaste, which makes it very convenient to use every day.
Overall, I would definitely recommend this MCT Oil to anyone looking for an easy way to add healthy fats to their diet. It is high quality, easy to use, and a great value for the price. I would purchase it again.
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on May 17, 2026
★★★★★ 5
Great product!
Size: 16 Ounce (Pack of 1)
This stuff is amazing! It is odorless, flavorless and does its job with helping boost energy and helping you feel full. I put it in my morning coffee and it gives me just the boost I need. I HIGHLY recommend.
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on May 6, 2026
recommand products
Bride butterfly design Women's Low Top Sneakers | customizable wedding date - Silver
69.99
Travel Package, Portable Toothbrush Organizer
19.99
Beach Towel | Just married - 'Riding into forever: Making memories one adventure at a time' - Pink
39.99
Hatching New Memories Chick T‑Shirt | Bachelorette Party Hen Night Tee
19.99
Mrs. Johnson heart design Women's Low Top Sneakers | customizable name and wedding date - Silver
74.99