I had one of these and a Vibrent 1794 resonator installed in a 1999 Audi B5 A4 30v. I ordered the exhaust shop to mount the exhaust to a 3" pipe because that's both parts. (Just one custom cat back). Now my Audi sounds like it has a V8 and within the first few hours I caught people staring at me. Me and my friend caught at least 100 people in the small torest town watching and we were only there for 20 minutes.