To demonstrate the point about the wastegate
This is from a UR-S4, but the principal is the same
The wastegate cap is held down by six nuts. The dirty white thing sticking out around the side is the diaphragm.
For proper operation, this diaphragm must be present and in good condition.
There is a large Banjo coupling on the side of the wastegate. This is pressurised, which results in the wastegate being opened as boost increases. In early UR, this was connected to exhaust gas from the exhaust manifold. Later models had this connected to the inlet manifold instead, but the principal is the same. As boost increases, the wastegate opens.
The cap on the wastegate has a small bore tube. In this pic, it is open to atmosphere. On my Ur, it is also open to atmosphere. In many audis, this is connected to a part of the induction system that is subject to a depression, or 'vacuum'. As long as it is not blocked, it should have little impact.
In the middle of the cap is a large screw, normally bonded with thread lock compound, and sealed with a plug. This sets the preload on the spring which is under the cap, holding the wastegate valve closed. if this has been tampered with, then the plug will be missing, and the screw can be turned (13mm allen key IIRC) if the load on the spring is too light, there will be less boost. if the load is too much, the car will overboost, and the built in protections will cut fuel to reduce boost.