I have FINALLY gotten around to mapping the GV controls as separate. Now that my flightstick has become looser than a ......(if I say it I get banned)...I have set my rudder deadband (i forget what axis) significantly higher for GV's. Problems with using a twisty in a GV can include extreme difficulty getting out of first gear, and as you mentioned, unplanned accelerations.
This completely solved my issue and may as well for you. if not Luche's plan of unmapping and using keyboard only will totally solve the problem.
Additionally I found that setting the other axis deadbands helped to prevent my tank sights aim from floating around, and for very precise adjustments I have found using the mouse to be effective.