Ethanol wouldn't contribute to knocking or pinging. Pure ethanol has an octane rating of 114. It's used as an additive in regular gasoline to raise the octane level.
My truck has run on nothing but ethanol E-10 since it was awakened from its Rip Van Winkle slumber 5 years ago. I've put 10-12 thousand miles on it in that time without any knocking or pinging. I regularly drive on the freeway at 55-65 with no lack of power. The engine has not been rebuilt.
Check your ignition system for a weak spark or any other issues.
You should also get one of Jon G's 200,000 hr condensers to insure a consistent spark. The condensers available today from any parts store are Chinese garbage that don't work properly.
https://www.stovebolt.com/ubbthread...oved-condenser-annual-update#Post1595503
