One note, not to drift aside the topic, but I have owned the Traxxas Nitro 4tec 3.3, and to say the least, if your not experianced with onroad & fast speeds, stay away from this car. The 3.3 in that car makes it MOVE, and I mean FAST! One thing I hate about the 4tec, is that its belt driven 4wheel drive & absolutly no belt protection from rocks & debris off the road, and the belts are a joke to replace...
Thats my .02 on that car.
Also, you dont need to make seperate topics for the same general question on engine type, you can ask all your RS4 needs on your original thread.