b. Most of the ethanol blockages are NOT caused by the gum deposits that cleaners are formulated to dissolve, but rather but aluminumcorrosion products, which then cannot dissolve. Thus, the solution is prevention. Use a good anti-corrosion additive.
Look at the bottom of the carb bowl. If there is any pitting, you have a corrosion problem. I used to have problems, but not in many years since changing to a good additive (and not all of them actually help).