in my opinion,its not really a matter of air fuel reading being different because your going to tune whatever octane fuel your using to the desired power and safety range, most tuners stay in the 12:1 range and you can achieve that with whatever octane your using, egt's can vary with octane changes if the rest of your settings stay the same (timing , boost), its all about deferring detonation, if you tune your car on 110, and then go put 93 in the car, its gonna run like ass cakes and will be detonating and knocking all over the place, higher octane allows you a much wider variety of timing settings, super high compression and boost options, you wont make a whole lot of power with 110 as opposed to 93 unless you turn up the boost and changes settings on the car, if you ran the same amount of boost on 93 and 110, truth be told ,youd probably make less power with the 110, higher octane is just a tool to help you make more power and let you have the ability to mess with things that can gain power without having to worry about detonating being a factor, unless your engine management is setup to let you swith back and forth beetween map settings at the flick of a switch( like the u-tec), then i would suggest you tune the car with the fuel that you will use more often, if your driving your car everyday, your prolly not gonna be filling up with 110, but if you can switch maps then i say go for it, just make sure you always have it on the correct fuel map....