One of the things about the stock exhaust, they design it for noise suppression first, then cost, then emissions, then performance. They are heavy and don't look or sound that good. They are tuned for all around drivability, good torque and good cruising. Aftermarket exhaust is lighter(usually about half the weight for a good exhaust), sound wayyyy better, look better, and are tuned for higher hp. This hp however may come at a higher rpm so if all you do is sick the exhaust on without making the correct adjustments in the cvt you won't see much of a gain. I mostly use aftermarket pipes for the sound, i love my scooter rumbling waking people up when I leave for work haha. An aftermarket exhaust is in no way a magic bullet, but its a fun mod for the scooter IMHO.
