Since it was so rainy at VIR last week, I needed an FGT track fix and drove about 125 miles on my home track - Nelson Ledges today. The FGT ran great!!! I gave rides to corner workers who have worked tirelessly all season and had fun. However, I noticed a black dust on my rear bumper and facia that I never have seen before. I also noticed that out of turn 13, a slow right-hander that leads to the front straight (and therefore is a pedal-to-the-metal corner exit) that the rear end "chattered", kind of like traction control was kicking in. Note that it was not loss of mechanical tire grip, as I typically rotate the car/tires on that exit. I assumed that the chatter was the differential - limited slip. With the black dust I am wondering if my clutch isn't up to the task of the sticky Hoosiers on a race course. Any thoughts and ideas? I attached a photo of the dust with my fingers running through for contast.