When you upgraded to the high torque servo did you upgrade to the correct servo saver. I had a simliar problem when I upgraded to a hi-tec 645mg servo. The stock traxxas servo savers DO NOT FIT on some aftermarket servos. They appear to fit but are not snug enough so when you turn you end up with slow and slippage. Make sure your using the right servo saver for your server, one that is specifically made to handle a hi torque servo...