If your going to mess with sprockets do the rear rather than the front, doing the front wears out your chain quicker.
Another mod you might consider and its not well known is to pull the cans off and where the two pipes meet at the junction you will see that one overlaps the other, it restricts the exhaust output to about 2/3rds flow... file that back to smooth and the responsiveness and smoothness improve... along with the sound.. its makes it silky smooth in output. Takes about an hour to do. I havent done it on my current VTR for lack of tools but Im hoping Spanish marty might have something lying around I can do it with when I meet up with him for beers... all in good time.
If you all are interested in the mod I will take photos to show what Im talking about. In the meantime just follow the right side pipe down and see where the join is... take off the can, look down the exhaust you will see it clear as day.. file that wombles down.... job done... easy... use the bike to clear the filings out - just start it up baby... job done.