Remember, the computer ignores the O2 sensors when you go to wide open throttle, so you won't notice any loss of power at WOT. But during 1/4 to half throttle, the sense of power might change, might not. Depends on what the a/f ratio is for that bank of cylinders.
Scott
MPG increase will be small but we all drive 5.0's so who is concerned with gas mileage? Just replace it and see! You won't have any power loss, if anything your computer will compensate for it and map to default settings for the fuel table.
I pulled my engine light because I am sick of changing $65 O2 sensors. My car runs fine.