My theory is that at low engine load the fuel pressure drops because the fuel pressure regulator is vacuum regulated. And this routine compensate for it.
that could be, i was under the understanding that little to no compensation is required for port FI engines with vac referenced regulators due to the fact it's just maintaining equilibrium between rail pressure and manifold vacuum (regulator is calibrated so the extra difficulty in injecting fuel at higher manifold pressures is accounted for).

will be interesting to see what it ends up being, if we ever even manage to find out - might be one of those calibration tables that we'll never truly explain.

the really cool thing is if it does operate in the low MAP ranges, it might be able to be jacked up and used for decel enleanment, which is another BIG HUGE GLARING THING that's missing from EE. right now, you have to jack around with timing to bandaid tune burbling and popping on decel with high overlap cams.

speaking of, could this perhaps be decel enleanment...? the determination of a state of decel should be able to be found easily, as at some point, it must branch on decel to kick into BLM cell 17.