Purchased this secondary throttle linkage for the Holley Sniper EFI system on my 68 F-100's 390 FE. Sniper by itself had the truck starting better than it had in my family's 30+ year ownership of the truck and it still ran as good as it did with the carburetor. System was showing one drawback in my particular usage, while it did good on the highway and even around town, throttle control was difficult at sustained low speeds.From the factory the Sniper EFI units open front and rear throttle blades at a 1:1 ratio. That's probably great for a big inch or performance engine, heck probably for 90 percent of users out there. The 390 FE in my truck is decent displacement but it's a driver not a racer, and speed limits around the "airport" I work at are in the 15-25 mph range with a decent amount of stop and go due to it being a high pedestrian traffic area. Throttles opened fast enough that it was difficult to maintain slow speeds and not enough usable throttle range.Installing this linkage (and making a few changes in the software) makes the throttle progressive, the secondary throttle blades start opening later than the primaries (44% on mine) and both are full open by the time it reaches 100%. It seems to have greatly increased low speed and cruse throttle control, yet still plenty left when I put my foot in it. I haven't taken it back to work since installing the linkage, but testing out in the county with light traffic, it's now much easier to feather the throttle and maintain low speeds.Probably not what you'd want for a "race car", but if you are like me and looking for a little better road manners at low speeds, this seems to be a great improvement.

Installed on my 4150 HP. Works and looks great.

Works on Holley sniper to give a more progressive throttle. Make sure to update the firmware. Plenty or instructions online. Fits nice, easy, cheap and effective.

Used to address the Holley Sniper secondary throttle plates opening too early under light acceleration and to increase gas mileage.

Easy install, and setup the throttle is much easier to modulate. But there is at times a hesitation from a dead start. Hopefully over-time the Learning app will fix that over-time.

Got 47% TPS on "primaries" with this. Did all the set up in the menus. Smooth bottom end with a good bit more torque. Drivability is much better. Don't expect much more fuel mileage.

Might work for some people but I bought it for my Holly X flow and even though it did help with the pull, my truck stuck with throttle on, on dyno. No good

Aside from having to crawl into my engine bay to get the old cotter pin off the Sniper, this worked great. Just be sure to update your firmware on older sniper systems and set the progressive value based on when your secondaries engage. Mine was 43%. Also make sure you have 60PSI for your fuel presssure... anything higher will make your sniper sound like a helicopter taking off (since its only using 2 out of the 4 barrels to pump fuel). I had 70PSI on my fuel rail. Installed an external regulator that I could set and helped a ton too.