IPE Innotech Performance F1 Edition (Valvetronic Exhaust System E90 M3) We kept the STOCK primary cats (We didn't do the IPE pipes) System is very quiet when the valves are closed, even on a cold start. With valves open, the car SCREAMS. It makes me laugh and smile so much. Hope this video helps if you're looking for information on an exhaust setup! I didn't find many helpful videos on YouTube regarding certain systems, so I had to make one myself! More information below!