[123pugsy]

Part description says 5/16" return line. That's the one in the center.
I thought 3/8 would be the pressure from the pump, 5/16 the return.

 

[123pugsy]

However, your air test says center in as it passes thru, and only doubles back when there is too much pressure (plugged)

 

[123pugsy]

One more thing, you're using the wrong clamps and 50 PSI is not fuel injection hose.

 

[123pugsy]

now if the new filter was different then i think the engine would not start or run correct. in the test photo one connection was putting air into the 3/8" port and i got no air for the other ports and the filter swelled up form the pressure not going anyplace and when i hooked it up with the air going to the 5/16" port i got air out the othe end to the engine and when i started blocking that port i got air starting from the 3/8" port on the tank side of the filter

This would be correct as there must be a one way valve in that filter. Never seen those before.