Me and my friends always get tickets for exhaust. The reason was always for being to loud. We just went to court with the smog and noise legal certificate that came with the exhaust and showed it to the judge. A bailiff would come out and listen to it by ear, He usually said its not loud at all. occasionally he would actually get a decibel meter and check. The test is holding about 2000 rpm for a few seconds. Judge lets you off after this. The problem is that when we get pulled over for loud exhaust a million other bull tickets are added on just because they can.