I've got an OS .91FX 2 stroke on an .60 size extra 300 plane. This is the biggest 2 stroke (and first ringed engine) I've ever dealt with. I'm turning a 14X6 prop and running 15% cool power fuel. If I adjust the high end needle valve just right on the plane while it's on the ground like all other 2 strokes, it acts as if i'm running it extremely lean by the time I'm in the air. I'll give it full throttle but it will only run at 1/2 power. I have to land my plane and turn the needle value almost a full turn richer to make it perform full throttle. When I give the plane full throttle in the air or on the ground at this setting, it sputters and eventually catches up. I like to have a good throttle response and good performance in the air but I can't seem to find the right combination with this plane. Has someone else had these same problems and if so, offer any suggestions?