Rather than suggesting I had the exact same problem, I was really suggesting that any deviation from the standard install can introduce both indication problems and operational issues.
In our case, I noticed on the first pre-buy run that there was no pressure indication with just the boost pump on. We knew it had a non-standard boost pump install so we checked the pump pressure later and it was working so we figured it was an indication problem. Got it home and dove into it. It had essentially two firewall forward fuel delivery systems from the firewall penetration. It had one line that went to the mechanical pump and then to the throttle body AND another line that went to the Holley pump then to the throttle body. The two systems were separated by one-way check valves. The fuel pressure was taken only from the mechanical side SO you never, ever knew if the boost pump was really working. We ripped it all out, installed a new AFP pump IAW the current drawings, installed new T&S fuel lines and fittings, put everything back the way it should be and all works perfect now.
So, I was only suggesting that you get the drawings and go through everything and make certain you are starting your investigation from a known point. You may just find a surprise somewhere!