How have the maximum torque or speed in a servo MG995?

I'm doing a minisumo and sought to give the most strength possible engines are connected to a 6V battery and 1 amp, the program with arduino library and work well only I seek to give them more strength. If anyone can help I would greatly appreciate it
sorry for misspelling English, I not speak English very well:C

I don't think there's much you can do to a servo to trade torque and speed: on a normal motor you would use a gearbox. Not sure if that's really practical on a servo.

Are these the drive motors for the robot? Not sure how that will work unless you converted to continuous? Maybe you should think of using a plain old dc motor with a gearbox.

Check the Datasheet for the Vmax and max amp. feed the motor with that current.

If it's not enought, get a bigger motor and match it with the a good power supply.