Originally Posted by Pokeyjoe
If you remove the SAI system, there will be less oxygen in the exhaust when the reed valves are open and the O2 sensor will adjust the mixture accordingly.
That's the official response. Some believe that "unchecking the box" in TuneECU only keeps the CEL from coming on.
My understanding is that the SAI will NOT open the reed valves when the fuel system is in closed loop mode as this WOULD, as you state, mess up the O2 sensor's readings and therefore the fuel mixture. Therefore, it would follow that removing the SAI will have no effect on the fuel mixture.