Mufflers

Apparently you can remove the internals of the stock cans for more power.

Some manufacturers include (not all make Hayabusa ones) :
Akrapovic - Arrow - Cobra - D & D - Hindle - Kerker - Megacycle - Remus - Staintune - Termignoni - TTS - Two Brothers - Vance & Hines -
Wolf - Yoshimura HMF

Sidekick Performance Silencers : According to them adds 6 HP. However I haven't seen where the improvements were made. The construction of these things look like a work of art. Like the use of multicoloured 0.5mm thick 99.9% pure Grade2 titanium etc... Try telling that to boys & gals next time you see them !! Their site can be accessed on the links page. You must check out the 'Alien' exhaust !