Originally Posted by DannyGT

It wont. My best friend has one of only a handful of supercharged RS4's and its using an M90. It has a pretty sick whine to it especially when you hear the car coming at you. Good news is - I had the pleasure of riding in a Rotrex powered M3, which looked to have the identical unit as mine, just days before I completed my kit and it sounded awesome. Its alot more stealthy sounding but during every shift you can hear the bypass valve giving off a sort-of 'laser gun pew pew' sound (ROFL). One thing we all agreed on was that it still sounded amazing, so worry not people...worry not.

My buddies RS4 for ref... YouTube - kryptonik8's Channel He made the video for his forum so its very detailed...just skip to the 8 min mark and you'll hear it. Same as that mustang. Ours wont sound like that, but he also heard the M3 and loved it...