The problem I think with the GT2835 KAI is with the anti surge slots. Stao from Hypergear PM'ed me about it and after explaining to me the theory behind the anti surge slots and how it could affect the power etc, I thought I would try a cheap fix for now so I came up with this:
Now after I put this on the car went pretty fuely under boost, i expected it to go lean if I'm honest but anyway. I spent about an hour tuning the AFR's to be a bit better (still a bit on the safe side but dont want to push it to hard yet) and played with maybe 2 or 3 cells of timing (under load)
I have knock sensor issues ATM which is why I havent added timing in. They give rediculous readings and I never hear a hint of pinging from the engine.
Anyway, Conclusion from the front swapover - The turbo seems to boost a bit smoother (if that makes sense), drive better, I dont have the "surge" issue I was talking about anymore, and I managed a faster 1/4 mile time and MPH last time I went for a race. (13.0 @110MPH, although I think its easily got a 12 in it if I get a bit more practice)
I managed 245rwkw with the old front, I'm waiting till I have some time to throw it on a dyno again to see if the front has netted some improvement to the power but from the feel of the thing I'd say it is better. Also the front is not sealed from the rest of the turbo. So I assume the high pressure from the anti surge slots that are now blocked may be leaking to the outside of the turbo(not to mention the possibility that this is causing turbuelence)
As I said however, This is a cheap fix and if it nets a power gain I'll be getting a proper front housing for it without the anti surge slots, A Pro S housing would be ideal