Hot Fuel Lines

Pardon my ignorance. How can a pushing fuel system vapor lock?
When it gets heated enough for vapor pressure to equal maximum pump pressure.

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if it can get out the carb vent, that greatly helps.

I'm not sure how predictable things are if it gets really bad - which can happen with fuels that are allowed high RVP.
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You'ld think it would all escape, but maybe not if the heat is there and the fuel keeps vaporizing.
And if its forcing the needle valve open, then what's happening to the fuel level?
Finally, what's become of the fuel that's in the bowl and going into the intake?

The last I can make an observation about.
This is screenshot from a datalog where I removed the air cleaner lid while idling (yellow markers on timeline). (Summer 2011)
Recording time in min:seconds along bottom.
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archived discussion from that time.
'Sasquatch' seen some similar phenomenon.
Why is the Air Cleaner changing Idle AFR?
I was doing more fixing than driving that year so it could have had winter fuel or some old fuel or both. Didn't think about that or maybe even know about the differences then.