The octane of the gas has little to do with the way these low compression engines run. BUT the ETHANOL content does. I had been running marathon 87 or there 91 both had idle/ die problems in all my gas engines(poor idle).
I went to a local chain saw shop to see what they recommended for the chain saws.
2 shops both said, " Citco premium is the only local sold gas with out ethanol to there knowledge". So I tried some, O what a difference. The idle was unbelievable better.
No more hard fuel lines, or swelled up ones either.
I my area a lot of difference brands of fuel come from the same pipe line, and I am sure that holds true for most of the country. so even when you change brands your getting the same base gas with just a different additive package.
Try checking with a local small engine shop, see what they say works in your area.
Another place to check is a good outboard engine shop. Boat motors suffer from the same issues with ethanol gas.