hey all my car is getting 13.5 mpg i drive the car in the city shifting under 2600rpm i have a k&n full exh w/o cats the car has always done atleast 15.9 in the city and the past couple of weeks its been dropping to were its at now i was looking at my o2s and i see bank 2 switching from .1 to .9 volts rather fast but bank1 is switching slower and barely going over .55 and no cel or codes what do you think bad 02 sensors?