You're telling me things I already know... I played with FMU's over 12 years ago on boosted cars.
There is a reason why no one uses them anymore. They're garbage and NOT needed because you can scale the injectors in the ECU and use the 1:1.
FMU's are a band-aid for NOT being able to modify the ECU that controls the injectors, that's all that it was designed for.
But hey, what do I know about any of this stuff. You went to school for it right?