I finally got to run the motor in plane. It took different needle settings to run correctly. 1 3/4 high end 5 7/8 low end. You are correct that the low end also affects the high end significantly. Both needles run on the same tube like a glow engine. The pump sucks. Motor transitions good. Runs if I point it straight up or down. But sometimes quits at full throttle instantly if I lower nose too fast from a nose high attitude.