RE: 4WD -> 2WD
I've run my MT and my SS in 2WD by removing the front drive shaft but I didn't get any benefits from it other than the tail end kicking out on a regular basis. If you are concerned with your front diff idling, you can pull the dogbones also. I had heard that you can pick up some speed in the cars by doing this but I didn't notice any.
Tripper