[Igovert500]

I think the law is up to the specific county. It is a hard law to enforce, as very few, if any, cops carry around decibel meters in their squad cars. I've been pulled over for my old car's exhaust, and the cop didn't seem like he could do anything but give me a warning. I feel like it would be a fairly easy ticket to get dismissed in court, as the cop had no grounds to prove that your exhaust was too loud at the time he pulled you over. Also remember many trucks are subject to different laws. Emissions, limited routes of travel, and other things differ when you drive a commercial vehicle, so sound probably does as well. Some trucks need 4inch open headers simply to generate the power they need to move their loads. Obviously the cops will target your friend if he has a sport muffler on his car...technically it's primary function is to give hp gains, but realistically it does better as an attention getter. If you drive with an aftermarket exhaust, getting the cops attention is a given, just don't drive like an idiot when they are tailing you, and if you do get a ticket for the exhaust...go to court.