Nagase and Joe:
(Nagase the passage you quoted about maxing out the turbine is incorrect)
The turbine side CAN flow more than the turbine "map" shows because that is only the flow through the turbine, the rest of the exhaust gases can flow through the wastegate. Even if the turbine is in the "maxed out" or level portion of the line, it's not really maxed out - if you move to the right along the line, even though flow is flat, pressure can rise, and the turbine *will* develop more shaft power for the compressor, and more exhaust flows through the wastegate.
The actual shaft power that the turbine produces is proportional to the efficiency times the exhaust mass flow rate times the pressure drop. To figure out the exact power developed, IIRC, requires one to look up the enthalpy of the exhaust gas (I'm an EE and my thermodynamics is a fuzzzy memory now).
The shaft power required by the compressor is likewise proportional to the air mass flow rate times the pressure gain, divided by the compressor efficiency.
With a given turbine/compressor/engine combo, there is a point where, as boost is turned up, the engine starts to show a torque curve that drops off more sharply at the peak power area (i.e.the % gains are smaller per add'l psi of boost near peak power vs lower in the RPM range). If
the compressor isn't approaching the choke region, it is the *engine* that actually "chokes" at the top-end as the turbine requires much more backpressure to generate boost, because it reduces engine volumetric efficiency. You will see this as sharply increasing turbine backpressure at the topend (I saw this with my GT2554 at >10 psi). At this point I think anything that improves topend breathing will "uncork" some hp, and it will be good for another few psi. This can be done with a more hi-rpm tuned intake mani, a larger a/r, or possibly retarded cam timing or duration.
(see discussion between me and Savington about intake manifolds and turbines. turbo manifold design
The question is, which mod doesn't give up so much low-end)
Joe, the "corrected flow" is just the flow referred to standard atmo conditions. It's a convenient way to quote flow numbers, or to plot flow vs pressure, because otherwise the plot will change according to temperature (and you'd have to plot a family of curves).