i hacked up my apexi N1 system to get it to a legal noise level and remove the 3" section from just after the cat so my exhaust starts at 4" off the turbo and is a true 3.5" all the way from the end of the dump back to where it exits the car. to boot its only marginally louder than a stock system and good for an easy 300+kw, so nice for cruising around town too as there is no intrusive exhaust noise the stereo has to overpower all the time.
loud exhausts only bring more attention to you and your car from all the wrong people and then you complain that they pick on you for everything they can (not saying the OP, just in general) or maybe im just old and cant be bothered dealing with all that crap for no good reason.