I just put one my Holley 750 DP and I immediatly got a lean backfire through the carb. I had to go up one size on the squirter to correct it. This was just blipping the throttle hooked up to a hose in the driveway...no water testing yet. It does appear to move more air, at least off idle, as I had to add more fuel. Well have to wait for better weather to check wide open operation.

Is this the first time the engine has run this year? If it is the backfire was probably caused by old gas.

and isn't "old gas" caused by Taco bell?

Hasnt been in the water yet but the backfire goes away with the stack off and comes back with it on. Had a pretty bad stumble as well as the backfire.

I have them on my Holley 850 DP's, and quite frankly didn't see much of any difference with or without them. I also changed from the "little" 2" tall filters to 6" tall ones at the same time. The combination "may" have netted 25-40 RPM on top at most.

-Greg