Are you asking/concerned about fuel control or boost control?
You really don't even need an SAFC. The stock ECU will give a generally rich a/f once you do the standard BPU mods and since that's "safe" you really don't need anything else; unless you want to lean it out a little up top for a few extra hp...I never thought it was worth the effot or money to do that. Once you eliminate boost/fuel cut, i.e. BCC, the stock ECU will take care of the rest. I think what you said about the stock MAP sensor is correct, but it doesn't come into play when controlling fuel at high boost/WOT. With a locked closed wastegate and racegas, mine went over 25psi a few times and it was still slightly rich; anything over 17psi I always ran racegas but in that 17 to 22 psi range it was always the typical rich a/f BPU condition.