That's not half bad indeed, and that engine is a nice runner.

For what it is worth: I had similar adjustments programmed on some planes but the adjustment would act on the solenoid, and that way of adjusting gave a noticably faster engine response. There is time involved in building up and bleeding off pressure, and that dead time is depending on the volume of air above the fuel. Full tank=fast response, empty tank is slower response.
The solenoid does not show that delay, making the engine respond faster to a movement of the knob.

Whether that is of importance in flight (with operational curves and such) I don't know. What I do know is that the muffler pressure rising and falling with RPM as opposed to constant pressure, was what was making THE difference between bench and plane. So the critical point of this set-up will be to determine the RPM-based part of the pressure correction curves.

Maybe it is useful to know what relation there is between RPM and muffler pressure for a given throttle opening and (slightly) varying RPM. Because I don't think that relation is linear.
Absolute values are probably less important, but whether it is exponential or not, and if so, what is the exponent...