There are many ways to do what you require and all of them will improve it a little:
1.- rewire with low resistance wire
2.- install a mosfet, a home made one is enough
3.- install DEANs connectors
4.- Use a lipo battery 7.4v 15C or 11.1v 15C, the more "C" the better response
5.- Install a high torque motor
6.- If you have an ACM replica, be sure to shim and grease the gearbox correctly
Hope I helped
