If I service my Audi at a reputable Audi shop in the area (Independant Tuning, Auto Select etc.) will this void my warranty OR give the dealership an excuse not to honor a warrantable item in the future?

I drive a 2006 A3 with CPO warranty that ends in 2012.

Thanks in advance.

 

When I purchased my car one month ago from the dealer I was told that as long I keep receipts for any maintenance done on the vehicle that my warranty will continue to be honored. That said, Audi has already jerked me around so who knows if you can trust them.