Hi Jordan, welcome to the club :)
Sorry to hear you've been having issues with your A3.
It's pretty difficult to give any kind of diagnosis without specific fault codes, but from what you've said regarding boost pressure, I've heard of it before where the turbo actuator doesn't open fully, and the turbo pressure sensor picks this up throwing the fault.
There is an electrical connection that goes into the actuator. I would try wiggling/cleaning this to see if it is the culprit. If so, once cleaned the actuator should open fully allowing full boost pressure and no faults (plus the correct amount of power :) ).
As I said, this is just an educated guess but may be worth a look! Let us know how you get on.