Not the biggest mod ever, but pop the snorkel off the airbox, i found it seems to help it in the higher revs. Might just be a placebo but im pretty sure its a bit faster accelerating after 5-6k revs. Cost nothing so give it a go.
I agree with what others have said, its not a powerful bike and so will not out preform a R1 or such in a strait line no matter how much money you chuck at it! No replacement for displacement after all
