I agree with the Gianelli stock+ or something similar will have a less offensive sound for cruising through the rv park (a lot of pipes are pretty obnoxious, even the small expansion chambers like the lil' shitter).
If you are single speed, it is possible you could go another route. Get Polini Speed Cases or bore the stock cases to fit a 46mm Pinasco or 46.5 Mallossi.
^Not going to pull like a variated bike, but depending on the weight of the rider it will get around just fine.
For single speed there are also some options for larger rear pulleys, lighter front pulleys, lighter clutch pads, stiffer springs... (Don't go crazy with the stiff springs)