[NoDOHC]

The speed of sound decreases with increasing altitude, so the mach number of a given velocity would be higher, yes. I forgot that you were tuning for high altitude. You will be moving less air at higher altitudes, so I don't know if that will offset the compressibility effects or not.

You are right, the throttle body should be the same size as the runner. Any change in cross-sectional area will not only adversely effect your Helmholtz resonance tuning, but will also increase pressure loss in the runner (hurt flow).

You are going to keep the two ports on the center iron, right? They will open later and close sooner than the P-port, which means that they will have no adverse effect on the P-port power, but they will allow the engine to idle and run successfully at partial throttle (all the p-ports I have seen have serious issues at partial throttle operation, they liked WOT only).

I really like this idea, it is what I wanted to do for a long time.

Keep up the good work!