Please bare with me here.
I got a tune done on my 1.8t 6spd with ECU ending in BC. Driveability is all good and smooth. Only issue I have is that the power surges under high load (WOT or close to WOT). The engine load percentages go from above 100% and drop to about 5% abruptly the back up. This is usually in the higher RPM ranges (4K-ish). I realize this is all vague. I have tried contacting the tuner and he is no longer responding. The boost pressure peaks at 21psi and then settles around 18psi. It's a stock K03 with a 3" DP and HF cat. I am running stock injectors. No misfires. Everything else is great with the tune.
I can do some logging and post it here - just let me know what I should log? I would appreciate any help. Thank you.

You are correct. It is a 2005 B6. 

The rest of the driveability is great. I suppose I should monitor the lambda sensors if it's running lean at high load. I just don't remember seeing anything out of the ordinary when I was logging with VAGCOM.

What is involve in redoing the tune for TT injectors? I have a set of those that can go in.

I appreciate the reply.

I would suggest that you read all through the 1.8t community tune thread, get familiar with the logging and reading/generating the logging charts that are presented there, particularly those of  boost level and injector duty cycle at higher RPM.   
http://nefariousmotorsports.com/forum/index.php?topic=6955.0

Note that the final .bin files from that thread should be able to cross-flash to your 2005 ECU and would be much safer that trying to run 20PSI to redline with stock hardware.

Search and read the documentation and forum threads and should find ample info for adapting larger injectors but your really need to be able to first data log before undertaking any tuning and hardware changes .