Just installed a pair of Hitec HSG-5084MG servos onto my rally drift. They have a transit time of .05 seconds at 6 volts! They're the "Fastest Servo Hitec has ever made" (src: Hitec website) and more than twice as fast as the stock servo. Only 26 oz/in of torque though, so combined you get 52 oz/in...still more than stock servo.