Can you change your stock baffle to a race?

1.  Can you change your baffle in your muffler to a race baffle to make your bike sound better/louder or should you just buy a slip on?
 
2.  If you can change the baffle to a race baffle where do you buy it?

    you can always drill out the baffles. if you are just starting racing (trackdays) you really dont need to do anything though