>>28453641 (OP)Some car reviewer of the time said they were the best sport sedan no one ever heard of.
That said, as previously pointed out the ZF 5HP24 has a 100 percent failure rate of the "A" drum (picrel) in which it splits horizontally along the snap ring groove. On a positive note that means you probably won't find an A8 now that hasn't had that problem corrected. Well, except for the really low-mile examples that you would need to be looking for in order for the car to be worth anything at all.
Also, as previously mentioned they do have a problem with the 2-stage intake runner flap breaking, not just the actuator (though that too) and that does cause enough driveability problems that it has to be corrected which wasn't cheap back then when you could still get parts. It might not be fixable at all now due to no parts, don't know.