Can change the pinion...that's about it other then a standard motor upgrade.
I'm not sure what the stock tooth number is on the ARE-2 but if you go for a couple more you'll get higher top speed but less acceleration. Watch for heat build-up when changing pinions.
You could also Draw up and get a new chassis, brace and shock mounts made in Carbon Fiber and make it lighter
But that would cost more then the car, prolly just for the chassis
J