have you have checked that you arent due the Fuel Pressure Sensor recall (not that I think its an issue here)?
reading your comprehensive reply. Im surprised your fuel press actual is ABOVE your requested.
forge shouldnt have an effect under WOT and you are achieving requested boost levels.
I assume you have tried going back to stage 1 (which the bluefin will allow) and the fault doesnt occur ?
FP looks ok in rest of range but have you checked your cam follower?
may also be worth changing your in tank fuel filter too?
the question in my mind would be why SC map is requesting a boost level the car (in good working order) cant achieve
either that or dropping the boost is just a band aid to hide an issue you havent found yet...
at the end of the day vrstu's the expert
(the other contraversial option given the way the bluefin maps are uploaded , in theory you could reflash to stock and get a stage 2 REVO or APR trial and see if it exhibits the same issue))