Changing out the mufflers and maybe using a real high flow air filter, will allow more flow in and out which Leans out and already lean EPA setup. Too lean will over heat the engine and eventually cause damage.
Putting on the rhineharts more than likely would require some changes to the ECU maps to richen the fuel delivery. A SERT is one option as is the Power Commander or Dobeck Techlusion (which I chose) any any one of other aftermarket options. Previously, you would pay the dealer to do the Stage 1 update from a cartridge at a set fee, this has changed. A SERT is required which is more $$$$.
The SERT allows the download of factory available maps for simple changes such as filter and exhaust, but also allows a second mode where a map is custom made using a dyno to see where fuel is in excess or a lean spot. The SERT has some cons such as high price, you have to shut off the bike each time you send a map change, and that you cannot see what map is currently in the ECU. The Power Commander is cheaper, loads on the fly and allows you to see the map you have and make changes. I opted for the Dobeck because it is simpler to tweak if you only need to adjust for smaller modifications and don't want to go the Dyno route. On my previous bike, I had a PC and it worked well, I just had some issues with Dyno tuning and driveability vs. peak performance. I am only looking for sound and driveability. I do not need to know what HP is being made. Certainly 110 in motor is making 80+ HP from the factory and that is plenty for me. I'll monitor the plugs and ride and then leave it alone. My 2 cents worth. Hope this helps. [smiley=nervous.gif]