A few more things you can try. remove the servo and take it apart, inspect close for any signs of moister. It would not hurt at this time time spray it down with some electrical cleaner. This will sound crazy but you can also submerge the servos in rubbing alcohal 75%. What will happen is the alcohal will absorb the moister, then evaporate. Do the same with the Rx. Also with the JR radio's I have had trouble with bad soilder joints, inspect where the crystal connects, make sure it free of corrosion and has a good fit. Then if the glitch is at WOT, inspect everything that may be loose, make sure that the throtle cable itself is not rubbing any thing. Check that you have the correct spark plug. Turbo would be better in telling you just what plug to use than I will. I have no experiance with the engine your running. I did not get to down load the vid yet but I will soon.