I can say that the AWE home made pressure tester with regulated air supply works great.

Test and / or replace the BPV's if they are original.

If no VAG, inspect N75 and N249 hose & wire connections.

Clear all engine codes, drive car a few times and VAG Scan for any returning DTC's.

Logging - Warm up engine and on a clear stretch of road with VAG connected, get on throttle hard in 2nd or 3rd gear from ~2K to ~6K RPM's while logging blocks 114 & 115 together. Block 114 will show N75 Duty Cycle which is controlling the waste gates and 115 will show ECU Requested Boost vs Actual Boost pressure. Don't forget to subtract ambient air pressure from the boost pressure readings or it will appear as overboost (when boost is working).

Block 3 is also good to log with 115 thru the rev range as it shows MAF g/s airflow thru your intake along side boost pressure.

The results of these tests should show pretty quickly where the lack of boost problem is.

http://www.ross-tech.com/vag-com/m_blocks/