I was thinking/hoping that the boost onset could be due to my 73mm maf and possibly the exhaust setup.
Again, with 95% DC you should be seeing 25+ PSI if not 30, regardless of exhaust/MAF setup. Doesn't take a genius to know that, mechanical or otherwise. It is the FIRST thing you should have noticed in your logs.
Not in this context, but rather in general.
In general positive deviation limp has nothing to do with the MAF; didn't mean to imply it was at all relevant here.
Whether or not positive deviation limp triggers could be due to a lot of things if the car is on the edge.
In any case, no point in even guessing here; if the car can't make boost at 95% DC, all else is a distraction until that is fixed. There is absolutely no point in obsessing over the interactions of a bunch of different things if there are fundamentally broken (and obvious) things to fix first.
Fix those, start again.