sorry to hear the issues Mark.
from my perspective 10bar drop on req vs actual isnt unheard of on a K03 car , so whilst it is happening its not necessarily the problem. Im sure I have seen K03 cars drop more than this at 4krpm and not spit fault codes.
Does the req vs actual recover as the revs pass through 4k or continue to drop/ flatline at minus 10 bar??
for your remap whats the max requested? (110 /130)
Did you fit any new parts just before the 'ring that may just have pushed the fuel limit ?
Id err with stokeballon on a supply problem on the LP side... but what do i know