Just taken a look. Well written and explained. For completeness with aftermarket efi you don't necessarily need a rising rate fuel pressure regulator but obviously it makes life much simpler! especially at high boost with smaller injectors as the injectors are not able to flow the required fuel at a what is effectively a lower fuel pressure (as you already know looking at the article).

Your testing completely echos what I was trying to say above (badly). At higher loads the fuel pump was drawing more current, this current would have resulted in a greater voltage drop across the series resistance (supply and ground connections/wiring).

At lower loads the voltage drop would have been far less. So had you just tested the wiring etc, using the tried and tested internet method you may not have spotted that anything was amiss with the pump and assumed the fault was else where. Was the fuel pump a straight cosworth item or an 044?

Did that make more sense? lol My point really was aimed at the fact that measuring the voltage drop across the supply for one car means nothing when applying the same basic test to another without at least knowing either fuel pressure or fuel pump current as the voltage drop changes (is not static). Naturally any resistance caused by the wiring will limit the current which can be drawn by the fuel pump also and the best method would be to suck it up and actually monitor fuel pressure as you did.

Rob