Do these things really help? Which ones is everyone using? I saw the SLP one is over $40 delivered.

 

i didn't notice anything with mine. If you can get one used cheap i would get it though. I've seen dyno's of a few rwhp off of them which wouldn't be to bad if you could get one for 25 bucks or so. I took mine out though so i could get more air to the IAC after my cam.

 

On Horsepower TV they dyno'ed a car with and without a airfoil and came up with nothing for a gain.