1984 300D Air...route of entry?

Hi all. Seems my car is pulling some air into the fuel system from somewhere. I can see tiny bubbles that gather in the clear pre-filter when I rev it up. She runs a little rough after a highway cruise too. I figured the leak must be somewhere before that filter. I have installed a new screen in the fuel tank and a new hose and clamp from the tank screen to the metal fuel line that leads to the engine compartment. Also purchased the fuel line kit and have new hoses and clamps on pre-filter in and out. All clamps are tight. My question is.... the metal line that runs from tank to engine compartment, is that a solid run or is it interupted with a rubber hose splice that I am not aware of that may be allowing the air in.

Thanks for any info offered.

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