My crystal ball is saying do a voltage check at the pump under load. Or if
you have an amp meter look for 2.5-3.5 Amp's of draw from the pump (low amps
= bad ground or broken wire's on +  /  high amps= pump dragging)

The only other thing I can think of is the copper washer that goes between
the check valve and the fuel pump is usually fatter then most (about 2 mm I
think) if this got changed to a thin one it could be the cause of fuel
starvation.

Good luck!

Jeff E.   Lilburn, Ga.
87'WESTY Weekender (BOXOBLOX)
87'GL