This is for information purposes. Performance improvements can be made in a variety of ways. It depends on what so of enhancement you want to do to your bike. In the Hayabusa's case there appears to be an increasing number of stuff you can try. Motorcycles these days have been designed with so many concessions to reliability, exhaust emmissions regulations, noise levels, and other mostly legislative requirements and so forth that most modifications result in breach of any of these criteria which the bike have been designed with.
Many performance enhancements can breach the warranty that comes with any new motorcycle.
Apparently you can remove the internals of the stock cans for more power . The best site for information on exhausts pipes is Martin's Hayabusa Page Heaps of stuff on performance and other tech enhancements which I don't cover. However I haven't seen where the improvements were made. The construction of these things look like a work of art. Their site can be accessed on the links page.