The law in MA, is something like "Any modification of the exhaust or emissions system, or tampering with it to make it louder is illegal." On the other hand, Ive had dual 6" stacks for several months now, and have been pulled over for them, but its usually just to ask where I got them!!! One occasion a cop asked if I had a muffler, and I said, I wasnt sure, because I got the truck with the stacks...And he just let me go.