So actual, real racing then.....in that case here are a few things you should do to your stock RS4 EVO 3 to help you makes it through a race. This is assuming your group allows you to race with upgrades to the car.
In order of importance
1) Replace steering turnbuckle.
The original seems to have been designed to pop of during crashes, so as, not to send too much shock to the servos. In actuality, they pop off too easily. Nothing worst than having a turn-marshall put your car back on the track with no steering.
2) The brake disc and pads.
If memory servers me correctly..this thing is a piece of plastic with metal brake pads. Once the oil from the gas gets on them( and you will get gas on them) say goodbye to smooth consistent breaking, if any at all. Get an upgraded brake disk similar to this one:
with a brake pad similar to this:
3) The Exhaust pipe.
For kicking it around the parking lot, this pipe is fine, but for racing around the parking lot you should definately upgrade to a better tuned pipe. it does not have to be top of the line but at least a dual chambered version.
This should be enough to see you through your race. Everything after that is up to you and your track rules.