The vapor lock problem with these is usually after turning off and trying to re-start after a short time. That is why there was a start valve modification.
But , in your case, [ while running on the highway], I suspect
a fuel problem because you changed the fuel pump and went
with a generic one.
The system requires the correct feed pressure or the pump will starve at higher loads and the return line to the tank will not funtion. This return loop is what keeps the fuel line both full and cool. If the pump you used does not have the pressure to get past the return line dampers [ there are 2], then you can experience vapor lock problems.
As a test on the fuel filter container needing an insulator, I suggest you first remove the two bolts that mount it to the motor mount , pull it clear and take it for a test. If that helps , an insulator can be fabricated by remounting with longer bolts and an insulator block in between the mount and canister. [ non-metal,of course]. I have also seen guys wrap the canister in f-glass insulation. A good one can be had at the dump from the side panels of a discarded oven or dishwasher. They are a glass construction, but are compacted to hold shape and usually have a foil back. Put the foil out to reflect outside heat.
But fuel pressure is more than likely the problem. Ck the pressures and compare to specs.