If any Audi owner or Mechanic is interested in how to test an Audi turbo system, I will give you a download link where you can download a pdf doc with all info like:
Charge air pressure control, system overview
Charge pressure bypass valve
Turbocharger and wastegate
Charge air pressure control (via load signal)
Charge pressure leak test with VAG
Performing pressure test
And much more tips Click http://www.petertuneup.co.za/files/Turbocharger system.pdf to download the file. Hope this will help