An FMF advertisement on Vital for the a new exhaust system for the 2018.5 KTM and Husky Factory editions got me thinking. How much better (and if so why) an aftermarket exhaust is vs a stock system. Do the OEM's really miss the mark when it comes to engineering everything to be great and then shit the bed with the exhaust system? I understand weight can be saved on the muffler, but what gains do companies like FMF, Pro Circuit, Yoshimura etc seem to find right away? Or are most people purchasing for looks?