If the TCC is either not working correctly or as in the following PCM trace shows, the TCC code was mucked with by a so called PCM tuner, the Torque management circuit to protect the drivetrain will disengage the converter to where your free wheeling ( T.C not connected to drivetrain) thus you lose overall torque since it is not under engine power.

The attached Excel sheet is from a trace with a A4 C5 owner who has had lose of performance since he has PCM code worked on.
He felt the car just did not pull very well. He did a PCM scan while driving and the results for this tread was sorted to bring all the cycles the TCC was engaged to the top of sheet showing loss of torque.

http://teamzr1.com/torqmange.html

Notice this occured during different RPMs.

Now here is a trace that was during WOT and TCC not being triggered.
Notice the higer overall TQ number.

http://teamzr1.com/wottq.html