Got Shell 93 Octane and now barely idles 1973 Dart 340

If you're not gonna burn it all out, add just what you need, on Sunday night. That stuff contributes nothing to combustion. It will also not rejuvenate old fuel. Once E10(all I know),goes Orange, it's only good in old lawnmowers and such like, with carbs that have adjustable fuel circuits. Or EFI cars with knock sensors. They will pull out timing to prevent detonation and richen up the injectors to compensate. Unfortunately they seem slow to recover after you put fresh stuff in, if you regularly drive deep into the power.
I have mixed fresh clear stabilized gas with red gas at a ratio to get Orange gas, and that will burn in yard equipment, where the red by itself wouldn't even start the item.

I am so looking ahead to see how this plays out.