a/f meter in car using 110 octane

crackedback said

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Swifter, start out by pulling 2 jet sizes front and rear and see what happens with MPH. Picks up, you went the correct direction. 12.0 is usually rich side for N/A engines. Don't jet to a number, let the MPH tell you if you are headed the correct direction.

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Crackedback is spot on here ^^^^^. Use all the tools you have to get it tuned, jet to maximum MPH, read the plugs, and check the AFR gauge to see if it matches what the plugs and MPH are telling you (it should be close). Once you know what you car likes, you will have the data to tune it down the road by just looking at the AFR gauge....but I would still jet to the best MPH, that method has never failed me. My AFR gauge is still pretty new to me and it is still gaining my trust, lol.

I don't think the octane of the fuel would have much affect on the AFR. The O2 sensor is just reading how much oxygen is in the exhaust gases as far as I understand it. I have a AF meter in my car as well, but since I'm on e85 the optimum AF ratios are different.