acy76--

I think that a lift pump pressure of 6 psi will be OK. The injection pump housing pressure is internally regulated at pressures ranging from about 25psi to about 100psi, depending on engine speed.

But, I wonder if you really need a lift pump? With your filter 'starting to empty' I think you may have a leak in your fuel line or filter head letting air into the system.

If you do install a lift pump, I suggest that you place it as close to the tank as possible. This will allow the pump discharge pressure to add to atmospheric pressure, making a more positive fuel delivery to the engine compartment. At the same time it eliminates any negative pressure on the inlet line which will discourage any air leaks into the line.

Of course, if you do have air leaks it is best to find and fix them.

Paul