John, it seems that the G90 uses the ABG function to establish the G2 setting. What I do is to turn on the projector and let it run with ABG enabled for twenty minutes. After that, the ABG is calibrated and the G2 value seems to be updated. If you turn off ABG after that, the G2 setting seems to remain constant. If you keep ABG enabled a new G2 will be established every time the G90 is powered on and let run for twenty minutes.
I usually turn off ABG just before calibrating gray scale. Then before redoing grays scale in the future I let ABG run again for 20 minutes.
If you want to find the settings in the Dallas chip I suppose you could compare a before and after with respect to ABG on and off. This way you could locate the addresses in the Dallas chip. I guess you would have to pull the Dallas chip twice though.