Update: the x wouldn't run unless I had my foot to the floor and even then, it was barely idling. Rail pressure check returned a 12 psi reading, so with the filter/regulator out of the equation(it was the original and needed changing anyway) I'm moving on to the fuel pump. There's no fuel leaking anywhere, so the fuel pump must be giving up the ghost. Unless I've forgotten something major, there isn't any other component in the fuel system, that would cause a low-pressure condition at the rail.