First up i have to say that i dont fly the blue flag i fly the orange flag so this question is for my bro. He has an 06 wr450. Now it has a staintune pipe and aftermarket jets but he doesnt know what size as it was bought this way. Now when you hit the throttle from idle or low revs to quickly the bike stalls. Is this a jetting problem? When the revs are up there is no problems.