I had a rs4 2 but its not really worth it to really upgrade it cause cost add up FAST. I'll explain why:
1. A two speed tranny, if you can find them, are about 50 bucks.
2. A better tuned pipe, 20-60
3. Rs4 2 Racing front end - iono, about 40 bucks?
you will probably need more, but i'll stop here because you can get a used ntc3 which is better in every way than the rs4 2 for about 70 used. A used Ntc3generally includes a 2 speed tranny, a tuned pipe, and it handles out of the box better than the rs4 2