I own a 1999 A6 Quattro 2.8L and just had to purchase a new alternator. I was going through the same thing...because I can't get in there to get it out to see the part number. It's too tight! Anyhow, mine was a 120amp....I would assume that yours is the same. I just called an Audi dealer, talked to the parts department, they pulled up my car by the VIN# and were able to tell me......
Have you tried this???