Vapor Lock........Haven't heard this one since the 70's. Kindda went away in the 80's with the introduction of EFI and pumps in the tank. Gas cap venting? Tank could be in a vacuum...
Yes, you can cover up the fuel line with thermal cloth, pipe insulation, an old trick was/is tin foil. All of these provide a heat shield for the metal fuel line. Another trick was to attach every four inches is a wooden clothes pin. One last trick is to replace the metal line with fuel hose, works well, but I'd use it as a last resort.
It might be worth while to troubleshoot the fuel pump, if mechanical. Check it for vacuum on intake side, and you might install a clear fuel filter to see if any bubbles are evident, as in a leak in the line from the tank to the pump. Clear filter should always be full of fuel.
If you believe the fuel system to be a problem, I would suggest installing an auxilary pump by the tank to assist the mechanical pump and/or install a return line back to the tank/"Y" into the tank outlet.
Well. maybe some others will chime in with their suggestions.....Good luck!!