Upgrade the WHOLE truck.....Only Kidding.....
What model do you have (21-25-SS)?
It doesn't really matter what model you have. The fist two essential things to upgrade would be:
1) Tires & Rims
Find something lighter - This will help out tremendously - You gain a tremendous benefit by decreasing the weight of the Tires & Rims. One is that you are decreasing rotational mass which is gives a greater benefit than decreasing static mass. Another benefit is that the lighter weight will also take off some of the strain put on your steering servo to turn them.
2) Steering Bushings
Replace the stock nylon busings in the bellpost with some ball bearings. This will also help your steering servo by giving them less friction when they are trying to turn.
:winnar: