I also uploaded my 2010 Nissan 370Z today. I needed it to be competitive in A class for a career event, but I wanted to upgrade braking and handling before I touched the powertrain.
Um. I think I screwed up. It's the scariest car I've driven in the game. Of course, I never shut off the nannies in Forza 3, so I'm learning to drive without TCS and with a manual transmission. My first race in it was at the Bernese Alps, and it would not stay straight at all. I didn't realizwe that the car had a 6th gear until the end, as I never got to that point. Scary, scary, scary.