Fuel line run question

All I can tell you is with typical 89 octain pump gas with ethanol my stock 273 dart would almost die after 50 yards of normal acceleration when the engine was hot on a hot day and you could watch the clear fuel filter fill with vapor ( kept pressure)

Then I switched to 89 octane alcohol free and have not had the problem happen again. And I have tried to make it happen. 98 degree day sitting in a fast food line in gear for 5 to 10 minutes is all it would take in the past. Now ideling in gear for 15 minutes 98 deg day. Then start driving and no issues under acceleration, even heavy acceleration.

Science is not always right in the real world. Way more variables there.
Weird...like I said, I might be missing something, it just doesn't make sense to me. For example, I run e85 (about 85% ethanol and 15% gasoline) and I have never had such an issue. I drive the car a lot on the street and the track, no problems.

Science is not always right in the real world. Way more variables there.
Funny! The second part of that statement (way more variables there) is exactly why predictions using science go sideways sometimes. You need all (or most) of the variables or you will end up in left field somewhere.

I'm sure I'm probably missing something, would love to know if anyone has any insight.