[ngoma]

2-5 PSI. Before the filter, to eliminate any possible leak there also.

The reasons for the temporary fuel pump:

The fuel route is under vacuum from the IP centrifugal lift pump section to the tank. Moreso from the IP to through the filter media. By placing the temporary fuel pump ahead of the filter inlet we are slightly pressurizing that section, eliminating the possibility for the air ingress we are suspecting is causing the stalling.

If the stalling problem clears up while using the temporary fuel pump, (I will also be curious to see what happens to the bubble in the clear fuel line section) but returns without it, we can narrow down the cause to air ingress leak and direct our efforts in that direction. Added bonus: the fuel pressurization there may show us the leak location with a "new" or more visible external leak.

Does the stalling happen early on in a journey? Or after an extended hard load high RPM run? Can you see if the bubble is larger when it stalls? Are there any visible fuel leaks at the top, sides, or bottom of the IP?

There shouldn't be any bubble in the clear fuel line section.

I wouldn't subject the fuel system to air compressor pressures. Too much risk of blowing out seals. Unless maybe you are attempting to clear out a suspected clogged hard fuel line between the filter and tank?