Here is poppers post from the tuning and faq thread. Its helped me, and my XP rages.

Probably one of the hardest things to do when you first get into this hobby is learning how to tune your engine. One of the problems I first had when I got into nitro was simply realizing what everything was and where the adjustment screws were. Well anyways, here's a picture of the adjustment screws.

The following are what the factory settings are incase you ended up tuning things to the point where the car won't start anymore:
High Speed Needle (HSN) - Turn the screw all the way down (clockwise) but don't tighten it. Then unscrew it 2 1/2 to 3 turns (Counter Clockwise).
Low Speed Needle (LSN) - Should be flush with the collar.
Idle Screw Adjustment - Take off your air filter and make sure your throttle is at idle. Then make sure that the opening in the carb is about 1mm.

Hope this helps. If anyone wants to add anything to this feel free to.