[Alpine TSi]

This may sound stupid but is the boost controller installed correctly? If it is installed backwards, the wastegate will never open and it will just keep building boost. If it is installed correctly it could be creep, but creep would be that the boost settles at where the controller is set and then goes up after a few thousand RPM. Also if you have the knob turned too tight the spring is too hard and will never open, so your wastegate will never open either. Just crank it almost all the way out and make sure it won't fall out, then give it a shot.