Well, if you want to know what you can do then here you go...
-Cams
-New cam gears (they have adjustable ones for bikes as well...)
-Ignition advancer (different weights)
-New Pistons
-Headwork
-etc...
-etc...

Almost anything that you do for a car can be done for a bike. If I were you I would get the different weights for the ignition advancer and then if you want to go further get some cams. If you are serious about riding/racing these are not "too far" I've been around many people that have done the things listed above and more and the argument that you have to do a lot of rejetting... That's bull! Since when has any good performance mod been done that you didn't need to retune your vehicle be it a car, bike, ATV, or moped!!! If you are one of the people that thinks that retuning is combersome then I would really suggest that you just stay where you're at. Or, do the best thing, BUY A BIGGER BIKE! If you just can't seem to squeeze that little bit of extra horsepower out of the R6 and don't want to retune a lot get a bigger bike. Either way hope these options help you out a little bit.

Later,

Sean C.

P.S. I have a way of sounding demeaning and please don't take this reply as one of those comments. This is purely for information. Later.