Still fighting off corn oil. However the gasoline available around here is only 89. Engine specs call for 91. Haven't added any octane booster yet. Do I need to use it?

Depends on your motor and your tune. I need 92 minimum so I carry Dragon Racing octane booster with me.

I have tested a lot of gas. 89 on the pump is the minimum rating. I have tested 150+ brands and octane ranges and in every case the octane has been 1 octane higher than is written on the pump. 89 Octane written on the pump is really 90 + octane, 91 octane is really 92 etc... This is true with ethnol or without.