To be honest your stock carbs already need to be re-jetted to improve performance and economy and you really need overflow tubes (do a search on Hydro lock)
The only thing your going to gain with slipons is less weight both on the bike and your wallet. You wont get anymore power than you already have other than the above recommendation.
Read this:
http://sites.google.com/site/shoodabenengineering/intake-and-exhaustIf you want the best value for your money do the Performance Exhaust Cam Sprocket and the Carb 2 minute Mod or get the full set of cams.
If you have money to burn and you just want loud and looks (you wont make any more power) Delkavic makes nice slip ons or you can get Dale Walker Hole Shots.