[Richard L]

The reasons for the boost incorporation:

Many turners still use boost only to control flow due to their previous tuning with boost based only system. Unfortunately all modern direct injection engines no longer use boost as a load signal. Actual air flow into the engine is the combination of the throttle angle and boost.

In your case, use the boost for compensating the manifold pressure acting against the spray pressure.

For SC engine the boost is actually useful and it is tied up with RPM. But I still recommend using Fuel Idc as flow control, it is more precise. It take account of the air temperature raise after the SC.

The HFS2 is no longer available, future uncertain.

The HFS3 is more suited for your application. You can configure to floe based on 70% IDC and 30% boost.