Your engine is running too lean.

When you tune the engine on the ground you need to peak the engine (full throttle) where it will run without sagging or dying when the nose it pointed straight up and held there for about 20 - 30 seconds. THEN, open the high speed needle ABOUT 1/8 turn (or a hair more). This will richen the engine up. When you get up in the air (or taxing) the engine "unloads". This means the engine runs faster and leans out because the air going through the prop is being "pushed" by the motion of the plane - it has less resistance. You need to compensate for this on the ground.