Hesitation, surging and crap mpg.

[elbrownos]

Carb icing is nothing to do with water in the fuel. It's humidity in the air that freezes.
The air temperature drops as it expands through a restriction (the throttle butterfly)
Moisture condenses out of the air and freezes in the carb.
Not saying there's any harm in putting isopropyl alcohol in your fuel, but it won't help with carb icing.