In VA if you modify your car in anyway from stock it;s altering it breaking the Law. If you switch to a Apex,Greddy any aftermarket exhaust on a Acura/Honda etc and if its not the equevalent in specs to stock then it's illegal. If it doesn't keep the same or lower DB levels it's Illegal.
I know as I have gotten to many tickets in my 13yrs of driving for my modified vehicles...