Hi...welcome to the Forum
I would probably check the fault codes that would be stored in the ECU as the first course of action.
Possible causes could be the Turbo variable vanes are clogged up and not moving freely, therefore flagging a code when on boost....common on VW / Audi.
Other possibilities are the EGR, Injectors, etc but I would definitely pull up the codes first. If it is any of these faults, you can use cleaning solutions to sort it at very little cost.
Cheers Trevor