Well, I ran a 2.5" straight out exhaust (no cat no muffler and headers!) and I did not get pulled over at all. I even had to ride next to a cop on the freeway for a few minutes and nothing. I atribute this to me not doing stupid things like flooring the car for anything longer than 5 seconds or so (to pass up other cars). In essence, I know how to keep it in my pants...
Ricer's with loud exhaust systems feel that they have to show off at every chance they get. After the movie I was cruising down the former street racing street, and in the oncoming lanes I saw an EVO VIII and a honda civic driving side by side. As they passed I heard the buzz of their exhaust, but nothing loud. Then about 10 seconds later I hear the wail of the civic with no muffler about 1/4 mile away. Think about that, any cop within a 1/4 mile radius could hear that guy and he's practically TRYING to get pulled over.
"its not about the ride, its about the rider" <-- yes i just quoted FNF3 lol...