Have you tested your fuel pump supply UNDER LOAD ?
They can test perfect with no load(idling) but when under a bit of strain the wiring can be unable to deliver the required amperage needed which will cause massive voltage drop.
Just hook some thin wire into the plugs on the pump before pushing the plugs back on the pump, trail wire through window hook up to digi metre and watch it as you drive, may give a clue.
Was the map sensor brand new or a known good one ?
tabetha