Thanks Fellas!
Ya, even me lookin at the diagram, and beenings it a PWM signal, it would seem possible to tap into the existing wires. I didnt think of that OutToLunch, I think your right! The OEM system was never designed for 2 pumps. IIRC there are 4-5 or more companys that make the "Dual Fueler" kits, as there called. They all have a "box" that splits the signal to run the 2 pumps, whats in there boxes, no idea. I remember asking if i could just tie into the orig wires, and they all said no, too much psi. It could very well be an instability issue lookin now, ECM cant keep up fast enough?
Im not entirelly positive but is/couldnt the PWM signal, although a duty cycle, be 0-5v variance? If so, in my head it still kinda seems like that signal getting chopped in 1/2, would still split the voltage down? Or dosnt matter?
One other thought i had is that maybe the aftermarket boxes in these kits are intercepting the return signal to the ECM and are cheating/adjusting the signal back? Maybe tricking the ECM into thinking theres too much PSI so its output signal is correct for 2 pump operation?