Oh...additionally, I've done this on all other bikes I've owned (usually a re-jet). And it does NOT cause your MPG to suffer. Rather it usually improved it.
Your motor works more efficiently. It actually works less for the same amount performance. The only issue is that once you see your motor perk up (improved throttle response), you may get into the throttle more which WILL cause the MPG to suffer.
KTM 400 EXC