Well a bit more testing today, now I can use 100% throttle I thought I'd test the exhaust manifold pressure again. At 11000 rpm and 8 psi I have 5 psi in the exhaust. This is a great number, indicating that at this boost level the turbine housing is very well matched!
So, I decided to do the machining on the compressor side to try and fix my surge problem. Its 11.43pm and I've just removed, machined and re installed it ready for a try tomorrow (weather permitting).
I should say that I'm looking for a fix for my set up. It may not be that the turbo is the sole problem, it could be an issue with a manifold resonance or design or something I haven't considered yet. But, if this cures my problem it may be of some help to others.
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