When we see a racer is getting frustrated chasing a setup by throwing tweak after tweak at a vehicle, we often recommend starting over with the factory baseline setup. The same often holds true for tuning a nitro engine. Instead of tuning and tuning, we recommend starting over with the factory settings.
If you have a Traxxas TRX 3.3 engine, set the high speed needle four turns out. To do this, use a small flat blade screwdriver to turn the high speed need clockwise until it bottoms out (do not over tighten the screw). Then back the screw out by turning it counter-clockwise four full turns. The low speed needle should be set flush with slide valve body which is the piece the low speed needle screw threads into.
These base line settings also work well for the Traxxas TRX 2.5 and TRX 2.5R.