Air definitely flows better with just about any aftermarket exhaust, even with the GSXR system. Unless you're going to mess with your airbox, then re-jetting the carb isn't required. Most people will do intake and exhaust mods at the same time, for increased performance. In this case, you will need to re-jet.
Some people do it purely for a sweeter sounding exhaust note but many of the aftermarket options are quite loud. The GSXR system isn't excessively loud but is definitely a deeper sound and a little louder.
Originally Posted by acesandeights
What are the actual benefits of something like a FMF Q4? Are there any negative impacts to performance (lose low/mid end tq/hp), reliability, etc.? Do most slip ons go on without jetting/carb issues?