I have been reading in depth any and all info I can find on the O2 sensor and I ran across this interesting side note:

By modifying the O2 position as we are doing here instead of modifying the electronics, under full throttle or heavy load the ecm resorts back to its factory settings and does not use the O2 sensor to calibrate the A/F Ratio.....This is great for our intentions because with a "Booster" or other After Market Mileage Increasing add ons we would not have to worry about the Engine suddenly going to a too lean state. When it resorts back to factory programed settings it is in "Rich" mode until the load or full throttle requirements are relieved.