hello, i recently purchased an audi a6 wagon and i love it (i had the same car as a sedan years ago too!) i don't like it quite as much as my new q5 but there are certain things i like about the older model! ...not the radio codes! it is the delta cc unit.
last time i paid the dealership lots of money to find out they were standard (or at least lots of people had the same as me).
radio serial: AUZ1Z6T8225939 it is a delta cc, i am not positive of the part number...