you could also be getting some vapor lock in the fuel lines somewere or in the floatbowls. Fuel will flash into vapor at around 70 or 80 degrees, if I remember right.
Any fuel line close to hot pavement, over them heater hoses, or just a plain ol' very hot engine compartment can cause all kinds of head achs...
Hot days like that , you can chase your tail around looking in all the wrong places.
Try to insulate some fuel lines were they pass heat sorces.
On those kinds of days it is possible to be down 10% or more in power.
I am surprised both you and the car did as well as you did that day