boost cut
You should ALWAYS do a boost leak test before tuning, but more then likely he didn't change the value for fuel cut like stated. Same thing happened to me when I got my first tune.
Well there is a way to find out if its a tuning/BCS issue or a mechanical issue with the wastegate. If you run a line directly from the turbo outlet to the EWG and do a WOT pull, the car should hit 1 bar exactly and hold rock solid. If that happens you have a problem with how your BCS is hooked up or a problem with your tune. If it makes more than 1 bar then you have a problem with the wastegate.