skrez , If the glitch only happens when the engine is running I dont believe changing from 4.8 to 6.0v is going to improve the situation.
I would check the throttle linkage to be sure that there are no metal to metal contact points ( clevis to throttle arm especially ) .
If there are no metal to metal contact points start isolating servos by disconnecting them one at a time and rechecking for the concern with the
engine running , this will isolate the cause to specific chanel where the interference is being induced . Possible causes could be a bad servo
pot effected only when the vibration from the engine is present or possibly a bad servo wire extension and the pin contacts are being etched by the
engine vibration .
Good Luck ,