By the way shouldn't there be 12 volts coming out of the inertia switch to the pump?

 

Your fuel pump always has 12 volts when the key is on. There is no pressure change thru the voltage suplied to the pump, it is controlled thru the fuel pressure regulator. As stated above the only down fall is not having a fuel cutoff in case of accident which none of the other big threee have anyway. Your fuel output is controlled thru drivers in the ECM, if I were you I'd be looking closer at that.

 

That's the other type - I omitted - a system that always pumps to full pressure and uses the regulator seperately. Actually it's probably more common than one electrically regulated.