Yikes. I guess thats one way to skin a cat. Are you sure you can make that big of a discontinuity (even if it is compensated for by KFLF?)
I'd always thought it would be better to just underscale the MAF as a whole, and have load be underscaled everywhere, not just in some regions.
This works just fine. I don't see the point to under scale down low, as I would lose fine grained control and blow up part throttle.
Overscaling up top is fine, because this thing has a 1 bar wastegate spring and boost is 30 psi anyway, so the transition is really fast.
That said, I played with KFLF quite a bit just now on the airfield, and I got my fuel right where I want it, because I am linearizing the PID, I also had to do this with 0, 10, 20, 30, 40 etc duty cycle and actual follows requested nicely. This is a narrowband ECU as well.
As for fixing the problem entirely - it will need a simple ASM hack. Before rlroh_w goes into the integrator and gets transformed into ps_w and pbr_w, it should be divided by 2, then multiplied by 2 again.
ps_w is not important, what is important is pbr_w, and keeping it lower until we get back to rl_w. Underscaling the MAP will accomplish nothing at all, because ps_w is calculated from rlroh_w.
When I get some free time (usually in winter, when we have snow), then I will probably write this hack into the ECU. I rewrote tons of stuff on the older motronics to suit my needs as well - factory systems don't really like more than 200hp per liter