Well, for once I'm happy that I live in PA. Our exhaust laws set specific dB levels to be met and an extensive test to be performed before a system can be determined to be non-compliant. Not only does it stop the BS "louder than stock" stops/tickets, it also makes an officer be darn sure he can make it stick, as he and the subject need to make an appointment at a State Police testing center to check the sound level. In addition, the levels are prety reasonable (in the high 70 - low 80 dB depending on speed - at a distance of 50 feet). I forget the specifics, but I know where to lok it up if I need it.
Haven't had to use that nugget of knowledge yet, but one of these days I'm going to hit the local police on a bad day and find out first hand how that test works.
