In answer to my own question -
I drove by every gas station on both sides of the strip in Wendover this morning, and they all had 91 as the top gas, no 93 in sight.
Had filled up with 93/10% in Twin Falls on our way in, and still had about 1/2 tank left. Not crazy about the 10% ethanol, but decided to run on it anyways. Put a 91 octane map into my ECU to be on the safe side, but fallback plan in case I couldn't make 130 was to add a few gallons of the ERC 100 and then run a 93 octane map.
Didn't need to worry. Ran a 134.43 on my first run, even though I was taking it easy on the engine, shifting 1000 rpm below redline. Didn't want a repeat of last year (two busted rods). Backed it up with a 134.48.
My dad ran the car this afternoon, and got a 133 and a 131 (bogged start), same gas and map. Oddly, though, there is now much less than 1/2 a tank left in the car.