Vehicle ID codes

[Joe Yakubik <75363.2524@compuserve.com>]

While flipping through my Maintenance/Warranty Book I see the codes identifying
(sp?) the equipment on my car  (I'm bored, ok, I'll get a real life next week).
Car 91 200 TQW, build date 8/90.  Third line id's the motor and tranny.  Mine
has 3B      AAT ADZ.  3B id's the 20V Turbo motor, which jives with the Bentley
and more importantly, with the car itself.  AAT and ADZ should be the tranny,
but no mention in the Bentley.  There's AOA, APZ, AUL, and AUM.  The ID number
on the tranny has ADZ 190?0.  Is this another of the exceptions/errors in
Bentley.  It is a 016 AWD tranny.  I assume the AAT refers to the final drive,
but this seems to tie up with and AGD tranny with older, weaker engines and not
the 20V turbo.  Is this part of Audi's continuing improvement without
documenting it within model years?  Do I have some sort of 90 and one-half
hybrid?

There is a point here, because I haven't isolated the noise from the drive train
yet, and I want to know exactly what I've got under the car.

Any help from the ID code gurus out there? (are there any?)  or maybe from those
who have been following Audi longer and closer than I?

TIA

Joe Yakubik