Im running a Scorpion de-cat with a non res stock exhaust on my S3. Also Apr stage 2 software, the issue is the car sounds horrible. Really tinny at low revs then once it gets to 3k to 4k it sounds like a really harsh metallic sort of rasp/rattle, then 4k onwards it sounds pretty good. Are they all like this? im going to re-install the resonator and see what that does.