https://njcourts.judiciary.state.nj..../part1_b_c.pdf
It's illegal in NJ and any cop can give you ticket if they feel your exhaust is too loud. I know many people received this ticket and I almost received one last week.
I think there's a fine line between "aftermarket exhaust" and "performance exhaust". When your dad's Honda Accord or your brothers Toyota Corolla exhaust craps out and you put on a aftermarket exhaust (non OEM) from local muffler shop, that's aftermarket exhaust. What we put on our cars are
Performance exhaust. The main goal for performance exhaust is sound (making it loud) and performance. Just my