I wouldn't mind if it overboosted to say 1.2 bar then held 0.9 bar, the boost seems to come down to 0.9-1.0bar in higher revs so may not be remapped. How does the ecu open? I have opened the ecu of my old calibra turbo to fit a chip before not sure if it's the same (motronic 2.7?)?
maybee a new maf and n75 would help?
or disconnect the n75 and put some sort of bleed valve in, or inline with the n75?
or get it mapped with bigger injectors