My concern with the above recommendations is that none of the companies responded to my requests for data on the effectiveness of their products. IE:
With A carbureted system,120 degree fuel in a steel line passes by a heat source like an exhaust manifold that is radiating 800 degree heat for 2 feet. The line is X inches away. and the flow rate is Y under the same controlled conditions
The fuel exit temperature without your product is ? A
The fuel exit temperature WITH you product is? B
Keeping in mind that with a carbureted system some of the fuel may be sitting next to that manifold while idling or cruising so the flow rate is critical especially at lower speeds / idling.

While I realize it may be hard to give a clear answer as there are many variables involved but a few "Static laboratory tests" would show / prove the effectiveness of their product.
I compare them to the thermal sleeves on spark plug wires that work for a short time. They do accomplish what they were marketed to do though, and that is GET $$ form your wallet to THEIRS

The one method that does work but is a PITA to implement is to run a return line to the tank with a restricted ID that will keep the unused fuel moving back to the tank while maintaining adequate pressure at WOT.
This is why the fuel injected vehicles don't have issues.

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