I've run my car with a MAF system, a MAF to LT1 MAF conversion, MAP using the TBI code as a basis, and now with a P4 MAP system.

I won't belabor the MAP to MAF stuff in T/C, S/C applications. But suffice to say a MAF can't see boost as executed in the 89 TTA. None of the MAF tables are related to rpm, so all it sees is Gm/sec., but that might be X gm/sec at y rpm, none boost and x g/s at z rpm and in boost, none boost is fine at 12.5, while in boost 11.8 would probably be better.
BTW, what lead to developing the first MAP conversion was generating a boost reference for timing and fuel, and the difference was very noticeable as to what the data logs showed.

But, in going from TBI MAP to P4 MAP and using actual gas laws there is again a signifigant difference for the better.

While working out the calibration differences to get a 749 to work in my GN, the idle PWs were way off. ie almost twice as long as needed. In quite a few test drives with the closed loop disabled, I would have for sure thought I'd foul a plug, but even with the tune so far off, the car ran well, as in really well for as far as things were off.

Some years ago I had run a TBi off of a 749 but it was long before to much was known about the 749 code, if someone wants to run a TBI off of a 749, start a thread, and I'll contibute a few of my notes from what I've found.