--Remove the snorkel from the top inlet of your air box.
--Remove the final baffle restrictor from your muffler (the one held in with just one torx screw, not the whole spark arrestor).
--Replace the o-ring chain with a standard non-o-ring chain.
Will end up increasing acceleration...Is this true?
Snorkel: Slight improvement. More noise. Must jet up.
Exhaust Tip: Don't take it out, instead buy a baja designs tip. Less noise than no exhaust tip, more power.
Non O-Ring chain: Slight improvement. You can tell a slight different on an XR250.