[toobroketoretire]

I believe that it may well be that the fuel is boiling as the symptom only surfaces when the outside temperature is over 100 degrees and I am in slow moving traffic.. Once it starts to "stumble", it is hard to restart if it stalls out. Other than that, it runs without any issues. It idles smoothly, no hesitation on acceleration and and starts up right away. I am thinking about installing intake manifold gaskets with the heat passage blocked. Do you have any alternative suggestions?

If it's just a case of boiling fuel you can easily solve the problem by slipping a piece of .010" stainless steel shim stock between the intake gasket and the exhaust holes in the heads (yes, you have to take the intake manifold off to do this). Brass shim stock will also work but stainless steel is burn-proof..................