hesitation stumbling on acceleration....STILL

[Bzoo]

Hey guys,,and girls too.
92 400E. New plugs, wires, rotors, coils,,all new vacume lines, tech 3 months,...dealer two weeks,...pressure at fuel rail 65lbs...hit the gas under load and the pressure is maintained or even jumps about 5 lbs...does not drop at all.
New maf but i did not do anything to tune it to the car. I read that it needs to be matched but Im not familiar with that. I thought it is plug and play. Slow acceleration and the engine runs perfectly...reaching cruising speed..perfect...only under acceleration either moderate or aggressive....aggressive is worse. Any ideas would be great.

Brian