You might have better luck posting this in the 4 cyl, section .
If your fuel pressure is still low then I suggest possibly a new fuel filter , or a new pump. You should be getting 35-40 psi at idle with the vacuum hose connected. I suspect its starving for fuel until you drop the hammer , then the vacuum drops off and closes the fpr.
90 LX Hatch, 5.0 bored .030 over/e303 cam/Ford Racing upper/lower polished cobra intake/ford racing polished 70mm throttle body/30lb injectors/ adjustable fpr/ 255 walboro pump/Ford racing aluminum x302 heads 1.7 roller rockers/bbk shorty headers with bbk catless xpipe/ 3.55 gears/tremec Z spec t5/ 5 lug conversion/Cobra front breaks/sub frame connectors/bbk upper/lower control arms