The fuel filter, the FPR and the dampener have all been replaced.
Electrically: Tested the pump itself, both old and new - both give readings in the "good" range. Tested the continuity of the wires between the pump and the control module and they all test out good. Tested the voltage running to the pump, and that's where it didn't match up - it runs constantly at around 14v at idle, never dropping to 3v like the manual says it should.
This is why we think it has to do with wiring somewhere.