I've Googled my *** off over the past couple of days on this thing. The VAG scanners are EXPENSIVE.... The car I'm needing it for is an 03 Audi A8L and it has TWO, count'em TWO, computers. One for the engine (ECU) and the transmission (TCU). According to what I've been able to find, the two function the same and should be readable from an OBD scanner.
I'm not going to get one of those cheapie things that just reads the codes. I want some that will give me details. The code reader that I had my friend use a couple of weeks ago to help me track down the misfiring cylinder (turned out to be a cracked spark plug) was a nice one you can get at Advance Auto. It was a couple of hundred dollars. I didn't notice if it had a USB connection though. The ones with the USB connection can be connected to your PC so you can print out the codes among other neat things..
I guess I'm going to be learning all about OBD in the next few days..

Cheers,
Dave