I second your plans to get a better turbo with lower EMP, curious to know what your plans are for this turbo. Custom made or an off the shelf option or secrete can't talk about yet?The next procedure is to replace the turbo to reduce the exhaust manifold pressure (EMP) down to 1:1 or hopefully less.
Because with the high EMP, it's a restriction in the exhaust and at above 10psi inlet manifold pressure the heat retention is ridiculous.
You could have the ultimate cooling system but under load on hot days it's never going to be stable.
Also just reading your reply the thought popped into my head that maybe 95% of people who would be interested in an upgraded cooling system would be running one of these "not so ideal" turbos with much higher EMP than IMP so I think seeing results with each setup would still be of interest.