I live in Oregon and 99% of the gas has added ethanol. This causes problems, not so much with my vehicles as with my 2-cycle yard equipment. Is there an additive which will reduce the impact of the ethanol on the fuel systems? Is “Star Tron” any good?
not really. It’s the ethanol itself that causes the problem, so you’d have to get an additive that somehow removed it from the gas.
Oftentimes premium gas doesn’t have ethanol in it. And there’s probably a gas station somewhere in your town that is taking a stand against that junk. Find it and give it lots of money 
Search the internet or ask around your town for stations that have no-ethanol gas, it’s probably available, you just need to find out what gas station sells it.
Ask people who are into older cars or other gas powered toys.
All of my yard equipment is electric now, but when I had gasoline powered yard equipment, I would add fuel stabilizer to the fuel as soon as I bought it, and I never had problems.
Modern 2-cycle engines tolerate ethanol with no problems…Ethanol has been added to gasoline for many years…
That reminds me, you can buy two-cycle oil that contains fuel stabilizer. Perhaps that would help the OP.
You’re assuming he has modern 2-cycle engines. My own chain saw has to be at least 25 years old.