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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 1464 reviews
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Product Reviews
★★★★★ 3
Can't choose the dino... sad!
I have a beagle/jack russel mix. Needless to say, he is very high-energy and does best when given a job to do that involves chewing.
He LOVES his Novabone and Nylabone- but tears thru the larger sizes in a single afternoon- so when I saw this I was very happy, because it is an unusual shape and durable! Amazon's iphone app let you scan in an item and find it cheaper on Amazon- so instead of the higher pet shop price, I scored a savings deal on Amazon! Nice!
My big, fat, sad complaint is that you cannot CHOOSE the dinosaur! I knew this when ordering and the stegosaurus arrived- honestly I was hoping for the T-Rex or the Brontosaurus but I guess you get what you get. Still, a beagle gnawing on a T-Rex would be pretty funny...
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Reviewed in the United States on August 13, 2012
★★★★★ 5
Great Toy for Teething and Strong Chewer
Eli is now 10 months old, a labrador retriever that proves time and time again he needs toys that he can chew, but won't fall apart. He cannot have the stuffed animal toys (no, those he'll tear apart in SECONDS, never mind minutes). Aside from the Kong and the antler, this is the only toy he can chew on that won't fall apart. Even animal bones will split in minutes.
Since he was a couple of months old, he has loved this Dinosaur Chew Toy. When he was teething, I'd put it in the freezer (sometimes put peanut butter on it to keep his interest). It was not only great for teething, but also massaged his gums. Now that he's out of teething phase, he still loves to chew on it.
For the money, this is worth it. It's saved the furniture and the house from being chewed on, as he focused on this toy instead. Highly recommend, especially for the price. For any strong-chewing pup or dog in particular, this toy won't shatter, split or break apart.
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Reviewed in the United States on May 15, 2013
★★★★★ 1
Cracked Tooth
Update: While I originally loved this product and so did my dogs, I feel the need to update this review. The Dura Chew Nylabones are incredibly hard, which is what makes them last so long. However, one of our dogs did crack a tooth recently from chewing on a Dura Chew. Since then, we have been very hesitant to allow any of our dogs to chew on these as other reviews also state that dogs have cracked teeth. We have since thrown out all of the Dura Chews that we had. We are still using the regular Nylabone products (when they aren't made in China), but once those are gone we will not buy any additional products from Nylabone. We have been buying Whimzees for our dogs for the last two years or so and they are a healthy edible alternative. They do not last as long because they are edible, but I have the peace of mind in knowing that my dogs are safe with them. Another healthy alternative would be antlers, which we also give to our dogs and they usually last a long time.
Original review: Another great Nylabone product. I love that dogs can chew on Nylabone products and they can't pull off pieces like products from other brands (Hartz for example). The Dura Chews are especially great for our hard chewers and they last forever! I love all of the dimples on their chews too, they're great for keeping our dogs' teeth clean. The vet is always impressed when they check their teeth.
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Reviewed in the United States on March 21, 2015
★★★★★ 5
Excellent for heavy chewers!
Flavor Name: Beef, Size: Mini
My dog is between 1-2 years old, and is a heavy chewer. So far the Better Bone is lasting very well! He still is chewing away at it! Excellent quality, and I appreciate that there’s no plastic that my dog is consuming.
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Reviewed in the United States on May 3, 2026
★★★★★ 5
By far ... the SAFEST and most DURABLE bone for dogs that are hardy chewers!
Flavor Name: Beef, Size: Large
After searching high and low for a NON-TOXIC, DURABLE and truly SAFE dog bone, I finally found the large, beef-flavored, HARD version of the BetterBone for my year-plus-old rescue (Carolina Dog).
1 - it's made of all NATURAL food-grade materials (cellulose from plant cell walls) ... which means no nylon, no GMOs, and no other artificials materials so it doesn't event stain your flooring. My girl loves the tasty beef flavor.
2 - the wishbone DESIGN is genius because it gives her 3 ends to choose from (nubs v raised edges v smooth) and ample ways to stabilize it on the floor with her paws.
3 - it is uber DURABLE in standing up to the hardiest of chewers (my girl gnaws on hers daily and sometimes even multiple 10-minute sessions per day). It works great to clean and reduce tartar on her teeth. The biggest surprise was that it took 6 months for her to gnaw it down to a size that was no longer safe for her (i.e. a potential choking hazard), so I donated it to a lady with tiny dogs at the dog park. At $20 per large bone, it's a good value.
4 - and most importantly, ... it is super SAFE. It degrades in tiny little pieces that could not possibly cause a choking hazard, and being all natural (i.e. no nylon - which most bones do have), there is no worry if she does ingest some of the particles. They vacuum up with ease.
The large bone weighs in at just over 12 ounces so it's kinda' heavy (9.25" long x 5" wide x 2" thick), but my 56 lb girl has no problem picking it up in her mouth before she hops up on the couch with me or into her bed.
Thank you BetterBone for making a superior product that is healthy, safe and fun for my pup!
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Reviewed in the United States on July 15, 2025