It’s pretty simple…the blower can drive a certain quantity of air into the motor. Added to fuel and spark and there is power to be made.
Put gigantic injectors, massive exhaust, great headers…and it is all somewhat moot if the blower is maxed out. The car isn’t going to make any more power.
The S4 world saw loads of guys who bought the M90 against everyone’s advice (it’s good for maybe 450 hp at the crank or say 375 WHP on an AWD B6) and whewn they hit the strip and ran within a couple of tenths of S4s with downipes, exhaust and JHM tune, they blamed everything but the blower in an effort to not be wrong. They said ‘I’ll show you all!’ and proceeded to add MASSIVE mod lists…only to have their cars then run the same times as when they just had the supercharger.
Superchargers are like big screen TVs…customer satisfaction is directly correlated to size. Buy a little blower, and you’ll soon get annoyed with its limitations.
Buy a blower big enough to blow your engine’s internals all over the county…get a good tuner who will keep your motor safe…give it good supporting mods…and smile. Buy a blower small enough that you are hitting the ceiling sooner than you want to and you’ll be frustrated and angry and end up on quattroworld (or worse, selling your Audi). Actually, no I’ve got that wrong. Quattroworld is far worse.