After work yesterday I went down there and filled up with the 91 ethanol free gas. I had 1/4 tank of 10% ethanol 93 octane in the tank. I left it tuned with the 93 tune and kept the radio off, and didn't hear any noise or have any issues on the way home. Either way though, I then tuned to the 91 tune when I got home(I chickened out lol).
I'm going to monitor timing advance at different loads/throttle positions for a while as is, then eventually tune to the 93 tune again on the same 91 fuel and see if it is retarding timing(due to knock). If i can get away with the 93 tune on the 91 octane I'm going to do it. Lower engine temp and colder plugs allow more timing advance, and I have the lower engine temp just need colder plugs(more safety margin). Maybe with that setup I could get away with it. We will see in time...
It's only about 5 miles out of the way form my trip home from work so it works out good. I'm going to start carrying cash though since they utilize the BS cash/credit pricing and charge $4.35/gal for credit instead of $4.30/gal like they do for cash. Considering I was paying basically the same price for 10% ethanol 93 octane, I'm happy with this.
They also have E85. Not that I'd use it but it's just neat they have a lot of different fuels there. The 91 ethanol free was a blue pump/hose and said "MARINE ETHANOL FREE 91 OCTANE FUEL" in huge letters. If anyone asks I'll tell them my truck doubles as a boat.
Breathing in and out is good enough for me.