Having turbo cars most of my life some things that I always recommend are:
Always have an AFR, always have upgraded head studs, always check how much knock you have under boost (this is cheap insurance as the cost for these are nothing compared to the repairs).
Under load, what was your AFR readings, 10...11..12 or higher? When under dyno, did you see how much knock you were hitting? Gas makes a difference (on my evo, chevron gave me 2 knocks while mobile 1 was over 7 (dangerous for me).
15 psi seems way too high for stock motor especially since these aren't designed to handle so much boost. What is our compression on these motors?
Finally you need a free flowing exhaust with that much boost and power, restrictions like baffles can be bad.
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