posted on a6 forum as well, so forgive the duplication:
Doesn't seem to be more than a glitch, but experiencing unusual acceleration in 3.0 '02 a6 quattro at around 3k rpm...feels like downshift, but i'm in triptronic 5th gear (shouldn't downshift in trip at all as long as it's in operating range, i figure); revs increase by 200 to 250 rpm; happens in all gears (in trip) once it gets up to around 3k. Anyone else with similar problem? Is it a vacuum issue perhaps? ideas?

 

Sounds like the torque converter is not locking up. @ low RPM's it will slip, even in TIP mode.

Your trans is not vacuum operated, it's computer controlled.

 

ok, thanks...wonder why both the engine rpm's and car's speed suddenly picks up at 3k; i would think torque converter suddenly fully engaging would cause rpms and car speed to go down momentarily...