What steveN is getting at here, is that a turbo is in two halves.

The compressor is one half and is the bit that actually determines how much air the turbo can flow and at what pressure.

The exhaust side of it is only there to turn the compressor side of it.
Now a bigger exhaust side can result in lower pumping losses etc to make the engine more effienct in using the boost, but what it cant do is change the compressor map of the other half the of turbo.

No matter what you do on the exhaust side, the T3 compressor (if thats what it is like SteveN says it is) simply will not be able to flow that amount of air without being right off the compressor map in a plcae with ridiculous heat generation properties that make it LESS powerful.



HTH