RE: carb does not return all the way
Alittle from the servo not really being good enough and some from the carb itself just being a tad quirky. If your going to keep the stock servo use a rubber band since it will give alittle easier on the servo. You can update your servos with stock traxxas ones or hitec even has some decent $10-16 servos and then you could use the spring and worry less about servo failure.