Start with 8541Hawk's "carb setup" thread- no matter what you'll have to get into the carbs, so may as well see what you have sooner than later. A baseline proven standard setup (like his) is a good way to go if it's been modified but you don't know how.

K&N plus aftermarket jet kit are recipes for trouble... not to say they can't work, but getting them right is not easy...

+1 on the 2500, this bike has deceivingly low torque which fools you into running it like a Harley, but really should be run above 3krpm like a proper sport bike.