The 2001/2002 F-car (Camaro/Firebird) files will keep the TCC locked when throttle is released (and MPH is above TCC Release curve)...
If your PCM is compatible with either of these, then try flashing one of these in (you will need to copy all your tables over by hand):
- OS 12202088 from 2001 F-car with A4,
- OS 12212156 from 2002 F-car with A4.
First copy all your tables over to the F-car file, then do a full flash.