Do you have an overpowering smell of gasoline? Overflowing float bowls?
That would be the indication of boiling fuel (other than engine flooding
and then dying).

How is your ignition timing? If it is retarded it will reduce power, gas
mileage and performance and your engine, especially the exhaust system, will run
very hot.

I think if your fuel was really boiling, you'd know it.
You might pull over quickly sometime and feel the float bowls,
also smell them. If they aren't WAY too hot to touch and you
are not getting VERY HEAVY vapor out of the float vents, your fuel is
not boiling.
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George Downs, Bartlesville, Heart of the USA!