I am guessing that you are running the throttle at low settings (i.e. the first third of the travel). In whixh case, if it is the needle, it will be the idle needle. I can't tell you which way to turn it coz I can't see the engine. The only sure way would be to unscrew it (not too much this needle is quite sensitive, probably about half a turn) then try and start the engine. If it is worse screw it in a bit (1/6 turn maybe, or 1/4) and try it again. Keep doing this until it runs better. When it starts to show an improvement reduce the amount you change the needle to very small amounts.

If after the unscrew it runs better, unscrew it a bit more until it gets worse, then repeat the above. I know this sounds stupid but you want it running slightly rich to keep the engine cool.

If you are at hover throttle or above it is more likely to be the main needle. The above procedure can still be used. Obviously this is more tricky as the blades will be going around. Unless you have the model secured at a height that you can SAFELY reach under the model you will have to bring the throttle to idle and stop the blades before making adjuctments.

(NB. By unscrewing I mean richening, I don't know if unscrewing is richer for your particular engine idle needle but it normally is. It is definately true for your main needle)