Gains to what extent though? An increase of 4-5 peak horsepower on a stock car isn't what I'd consider a worthy investment. The problem with the aftermarket offerings, is that none of the aftermarket intake manifolds start making power until the higher regions of the power band and the stock cams sign off too early to take advantage of it. Do a google search, many guys have installed the PP manifold with less than stellar results. And what you gain in horsepower, you lose in low end torque (where these cars really seem to need it the most). That's a lot of scratch for horsepower you're never going to feel. Might as well just buy a set of under drive pulleys for gains like that and save yourself $300
Take into account independent dyno testing done my AFM
http://www.performanceinjection.com/files/piProduct/DynoTest-54060.pdf
The car made 20hp/16lbs ft more than stock with the PP manifold, inlet and 70mm throttle body, but most of the gains were accredited to cams previously installed.
That's over $1,500 worth of parts and labour for only 20hp. I don't know about you, but that would kinda sting me a little? That's more than 1/3 of the way to the cost of a supercharger, for only 1/6 of the gains.