It's braided stainless hose so it shouldn't be sucking shut.

Today I took the line off the lift pump and put the air compressor hose to it. It pressurized the fuel tank no problem and fuel started flowing out like crazy so I'm pretty sure the line's not clogged.

I replaced a 90 degree elbow right before the LP with one that was a little more gradual which seems to have helped but it will still go to zero on a hard punch. I figure with 2/3 the cylinders you guys have the pump shouldn't have a problem.

I tested the vent and it works fine. The truck idles at like 18-19psi now which is like 1-3 higher than before.

Is it okay for the IP to see <1psi for a few seconds or am I going to need to beef up the fuel system?

 

I don't like to see them that low, but it doesn't seem to hurt anything. There are lots of guys with cranked pumps and a stock lift pump, they gotta be going negative under load and the pumps don't seem to die any earlier.