I'm a little confused...if it's overboosting due to the TD04 wastegate not being large enough to expel the necessary exhaust gasses to effectively limit the boost pressure, how would a simple tune fix the problem? Sure a tune will move/remove the fuel cut, but the car will still be overboosting.

In my eyes the only real way to fix the problem is to either port the wastegate on the TD04 of get a larger turbo.