Ok who knows how to read a compressor map and properly apply the size and controls to max the power?

As I see it to obtain 360cfm from the WRX turbo at a pressure ratio of 2 the wastegate must open at 22psi. This is the only way I see to get the turbine to spin up to the 150000 rpm needed to hit the target mark. If the wastegate is actuated at 14.7psi then the max rpm would be like 123000 rpm. With that said what keeps the the turbo from running beyond the choke line at at given rpm? I am missing a key point.

I assume Pr = (Patm + Pout)/Patm (neglecting plumbing losses for discussion) and the wastegate is actuated at the max specified Pout.

I also don't see how to keep a turbo operating at the optimal efficiency. If I wanted to keep the turbo on the 70% island how could I do it?

Help me out because I am missing something simple and key.