Re-jetting is not required, but it is a good idea if you want to reach the full top-end potential or if you feel that the driveability has degraded.
Here is a thread on BWB with lots of suggestions on Blast jetting with aftermarket exhaust: http://www.badweatherbikers.com/buel...0164/6812.html
Don't forget that you also have a jet needle for tuning of the critical mid-range area, if needed.
Let us know when you make the purchase, and post a few pics when you get the chance!