I have been in one Supercharged Z3 that made absolutely no sound whatsoever. I have a cone filter, big bore throttle body and a Remus exhaust on my supercharged 1.9, and it screams, literally. In fact, the sounsd is one of the best parts. At idle it is arelatively silent, so if you are looking for stealth, the suprcharger ywould fit the bill - it only makes itself known after having been suckered.