Audi are smarter than that. A box will cause certain parameters to be exceeded, ECU will store a flag and void your warranty on most mechanical bits.
The new flag is something like td2 or whatever the code is. It’s suspected tuning box or similar has been on the car. The car is flagged without you knowing just like a td1 flag.
It’s only a problem if something goes bang and there’s a big warranty claim.
Things like boost levels, torque on the gearbox etc have values stored on ecu and other electronics. If these stores values exceed what the allowable tolerances are then they might not pay out on warranty as the standard ecu should not allow these tolerances to be exceeded.
Other things they check is the connectors/plugs to things like fuel rail sensors and boost sensors as most plug and play boxes has to connect to these to work so if there’s any marks or wear on these connectors and plugs it further proves that something was plugged in and removed as these should not be connected/disconnected during service and if you had a problem with them before they would have a record of a previous warranty claim.
I had this confirmed to me by an Audi tech as tuning boxes are getting more and more popular as the selling point is remove it and Audi won’t know when something breaks. They will refuse to pay if they think something has been there. They have caught on to this.
Diesels are the worse as increase power comes with massive increase torque so chances of gearbox issues is very high.
Only possible good thing is the memory on the ecu/electronics is pretty low so if you drive about for a week or so before going in they could be cleared as newer records will replace older ones.
Only possible if you didn’t blow a gearbox or engine though.