Small update here. Finally found out why I was having such a hard time making over 20 to 21 PSI. No matter what I did I could never track down the "boost leak".
Turns out it wasn't a boost leak. It was actually the wastegate arm - when I initially put the turbo back together I counted threads and measured the length of the wastegate arm to return it back to "stock".
Turns out this isn't accurate enough for EWG vehicles.
I had a friend of mine who is a BMW tech run the EWG calibration procedure and turns out my eyes and measurements were off by 2.55mm! I'll be having this fixed next Wednesday by BMW and be back on the road datalogging!