For the 550 upgrade, iirc only changed sc pulley, belt, intercooler, injectors, fpr and sw. It kept the 500 crank pulley. Maybe Z4M have different crank-sc combo for the same boost due to space issues.
I think you are seeing the same boost as mine around 1000rpm earlier. And you notice more the boost due to sooner torque.
Can you say how much boost would a 5.31 and 2.87 make at 8000rpm?
