Re: External Fuel Pump?
I had a similar problem with my 93 bronco. When I shut the vehicle off, the pressure would drop to nothing. I only have the in-tank pump, but found that there is a check-valve in the pump that keeps the pressure at 35-40 psi when the vehicle is off. I had to replace the pump ($85) and the problem was solved. The symptom was the vehicle was hard starting if I didn't let the pump "pressure-up" the line before starting the vehicle. It was more annoying than serious.
This could be the problem. Another cause of this problem could be a leaky injector, or a hole in the fuel line. It may take some digging to find the problem. If it is a hole in the fuel line, I would definantly fix it. If it is a leaky injector, or a bad pump check-valve, I wouldn't fix it unless you have the time to spare and it starts getting annoying. Having a shop do the work will definantly "break the bank".
Hope this helps