I just thought we can offer you something based on boost only, you need to get a
2-bar map sensor.
It is the HFS-2 or HFS-3, operates in MPS (manifold pressure sensor) mode. You can set the start point and it will be progressive with boost from this point on. You can set the flow increase per psi with the onboard "gain" trimmer.
The HFS-3 is the same as the HFS-3 but with a dash gauge to monitor flow.
The HFS-2/3 is PWM valve based, so you will have fast response and good dynamic range. Sorry I have forgotten the HFS-2/3 can do this.
Here is the
link to the user manual,