I saw the section of the manual that said to input 8s. I uploaded each of the dynojet fuel maps, including the stock map that had all 8s in the necessary sections. It didn't change anything for me.
The o2 optimizer is definitely plugged in line to the o2 sensor. I disconnected it and the only difference is when I start the bike, the FI light comes on immediately instead of appearing after a minute or two like it does when it is plugged in.
There is one more piece of information that may or may not be relevant. The bike had been sitting from September to March and I have no idea if the original owner put stabilizer in the fuel. I took the bike for a ride last weekend and the FI light was always on. At the end of my ride, I stopped for fuel and put in about 2.5 gallons of fresh gas. Interestingly enough, when I started the bike and drove 15 minutes home, the FI light never came on. After I arrived home and the bike had been sitting for about an hour, I started it again and the FI light came back on within a minute or two.
Is it possible that the old gas is causing the o2 sensor error? My plan is to ride the bike until the current full tank (50% old gas, 50% new gas) until it is nearly empty, then fill with all fresh gas. Maybe it'll resolve itself...