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I think the problem to do this is that the rear motor in AWD is a smaller one vs. RWD. So the hardware limited what software can do. Potentially the P85D or P90D can do some of this but likely not as fast as it would be on AWD.
Btw, I just ordered my first Tesla: a 60 RWD. Have been back and forth on a few options but eventually decided on what I originally selected. Someone said in another post that every Tesla is a great car to drive. So I stick to what's important to me and what I can afford. Getting very excited and can't wait for the delivery in late Sept.