250 SX pipe

A lot of variables to consider...rider skill. Ambient temps. Terrain..sand/ hardpack ect. Fuel. Engine otherwise stock? ..if your bike is anything like my 18 250sx. It needs 1-2 next leaner pilot jet, and 1-3 next richer main jet, this applies to the bike no matter what pipe & silencer you have on it. Be consistent with your fuel & oil mixture so you can work on the jetting. I would also ask Pro Circuit for jetting tips, although I wonder if they have any real world testing on the 2t.

^Agreed, I had to go leaner everywhere but the main jet. I have HGS/ Bud Racing exhaust but I use a 450 or 460 main jet depending on track and conditions/temp.