Hi Jim!

TO4 is a frame size.  Kinda like saying "small block".  That could be anything from 265 to 400 cu-in.  There are 10 or 12 different readily available compressors, 5 or so turbine wheels and a dozen or so different turbine nozzles [housings] available,  You have to decide on boost for take-off at low altitude, boost to "normalize", or a combination/compromise before picking a compressor.  There are no compressors that will do it all perfectly.  There will probably be some parts swapping to optimize the
turbine housing [nozzle size].  That's like establishing the right pulley ratio on a belt-driven supercharger.  This step is usually overlooked leading to "less than optimal" performance.  It is NOT something that can be calculated mathematically.

Generally, the correct combination for steady-state is divergent from what works for best acceleration.  For us, that would be the correctly selected compressor, hooked to a comparatively large turbine.

The [terribly powerful Mazda exhaust] pulse thing, probably turds.  [pole vaulting over rat ...]

The wastegate must be able to be open at "no boost", which mean the ubiquitous pneumatic 'gate is useless, except to prevent overboost.  You have to be able to open the throttle fully to get atmospheric performance, and then close the gate to bring in the turbo.  I can't see anything that will work for that except a manual gate, or perhaps something MUCH more sophisticated than we can build.

You would like to have the turbine sized so that even with the gate closed at WOT, you cannot overboost.  This requires the turbine swaps [tuning] I mentioned earlier.

Most folks will be really happy with the performance 40-inches MAP will provide.  50 MAP is certainly safe with AV-gas and an intercooler.

Hope this helps [and you can publish it to "the list" if you like.]

TT
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Jim Sower
Crossville, TN; Chapter 5
Long-EZ N83RT, Velocity N4095T