Just a random thought, could a poorly sealing gas cap effect the fuel pressure of the system?

 

No it can't.

 

on older vehicles that are vented through the cap a plugged vent will create a vacuum in the tank and starve the engine of fuel. old school trick was to loosen the cap and see if it ran better. I doubt anything with fuel injection would have issues like this.

 

Not on a 22R with a carburetor.

A carburetor is more about fuel volume than fuel pressure. The stock mechanical fuel pump only has about a 4-6 psi output.

What does affect the fuel system is the float level.