If the actuator was mullered then the boost wouldnt hold, as has been said concerning a mullered dump valve.

Cant see how the wastegate can stick unless something is bent/twisted etc.

The boost is closed loop on P8 isn't it, so therefore the ECU constantly monitors and adjusts the amal valve doesnt it? It hasn;t got a bleed valve or been chipped has it?

To get 296ft/lb (assuming the reading is accurate) and the car is standard, it will have to be boosting a fair bit higher then standard.

I doubt very much that the ECU can compensate on ignition for that much boost on a standard set-up!