on my 899 i used to run Green cotton induction from a 1.2 punto, also a mckrich chip worked great too made it much nippyer in the 1st 3 gears but also made it drink petrol like theres no tomorrow.
also just remove bits to make it more lightweight ect... depends what you want performance or looks?
ifperformance take rear seats out and strip everything to minimum less weght = more power
or looks then youll need everyhting in still more wieght = slower accelleration
but its a 899cc the engines are tough as nails (i know this as ive had mine nearly off the clock) and it still runs perfect.
all i can suggest is service the engine, new plugs/leads/oil/oil filter/fuel filter/exhaust system/decat (needs to be on for mot though)
other then that then youll be throwing money away at engine mods as in boring out ect...