sorry to hear it..... I think the mineral power steering fluid that are in these cars cannot handle the heat created under the hood. Probably over heated it with the track time which caused it to some of its lubercating qualities. Really sucks... these cars should be able to handle it, since it is supposed to be Audi's highest performace model.
I have to take mine in for it to be changed.... good luck.
Sounds like time for a dedicated track car