The clue is in the "LPT" bit - Low Pressure Turbo.
Most only run to about 4-6psi from what i understand and the HPT runs to about 8-9psi.
The other question is, do you really mean boost cut? That is controlled by the ECU and (depending exactly how it's set up) cuts the fuel and/or spark when boost exceeds a certain level.
It sounds as if you already have an HPT wastegate in there, allowing it to boost to 8-9psi, i might be wrong on this as i'm not that well up on the turbos - i subscribe to the "there ain't no replacement for displacement" theory!
