I put a Vance & Hines SS2R exhaust header and did the Dynojet carb kit with the separate air filters on the carbs. The sound it makes through the separate air filters sounds better than the noise from the header!
Overall performance gain was noticable in 1/4 mile times and speed. Prior to installing the performance parts my times/speeds were in the 12.2-12.3seconds/111-112mph range.
After the above parts were installed, my best time was 11.62/115mph with consistent times in the 11.7 range. I had also removed the mirrors which made about a .1 difference from what I could tell. My driving also improved so I would guess a bit of the gain woud have come from there as well.
My bike is streetable and my performance increases were decent but worked well for my application.
Good luck on your performance quest!