no FCD on my MAF, wiring is all stock.
found more power with timeing in the mid range, witch translated to more power in the top end also. if we added fuel, the power dropped. not a lot but enough to make it unnessacery to add any more.
i just looked at one of my older logs. with the ViPEC, TPS 100%, RPM 8640, Iinector DC 86%, timing 20.2, MAF 4.75v. so yeah it is maxing out the MAF.
this is with the ViPEC not the Z4, but i would assume it would be about the same... good thing the ViPEC uses primarerly MAP not MAF.