Re: Upgrading Turbo in GT,
kgb has fitted a GT2256v from a 2.4jtd, its a fair upgrade as yours will be a 1749, so an extra 7mm on the compressor wheel and quite a bigger housing.
One of the problems with these small housing VNT's (15xx-25xx) is they can't handle massive boost (don't expect a reliable 2bar or higher), its quite common for them to baloon/swell which results in the shaft splitting in two and the compressor wheel becomming detatched. This happened to my gt2256 when we ran it at 2bar!
But you will certainly gain in terms of flow, and slightly higher boost than the stock provides.
Its always worth chatting to a decent turbo centre which specialises in hybrid/upgraded turbos.