Part of your promblem may be that as you are running on-road, and have a wheelie bar to aid traction, when you mash the throttle you will be send a huge current spike.
You can run more/bigger capacitors to help balance out the power delivery, but you are using big motors.
I'd suggest trying something like a 1/8 esc such as the Tekin RX8 (or similar). They will handle any 540 motor no problem.