The quality control for Gms seems poor,bearings wear out fast,some carburators don't work,some crankshafts are different than others[causing major vibration problem],and it seems only1 out of 4 of them can be shut off from the transmitter.
Speaking of GMS's on spads they always sag on a high G turns and you have to run them out of gas to land because they will not turn off.Mufflers will break fast if you have one with a bad crank.If you wear out your bearings in a couple months don't count on any warranty.
GMS's problems have nothing to do with tweaking the needle valve.