Originally Posted by 1997_LeSabre
If you have a narrow band O2, an air fuel gauge is pretty useless. The range that the sensor tolerates as 14.7:1 is so narrow that your air fuel gauge is pretty much either going to be pegged rich or pegged lean at anything other than cruise conditions. You'd be better off adding an auxiliary wideband O2 (find a factory app. that uses a wideband and find a sensor on ebay). A factory narrow band sensor is designed to switch lean/rich only to achieve 14.7 to keep the catalyst happy. It really won't tell you that much about your tune.
i wouldn't render it completely useless. You can see if your WOT O2'* are low, see if your O2 sensor is getting worn out, and recently i was noticing a situatuion where i was loosing some power around 2500 rpm and i looked at my narrowband o2 sensor and it was showing a lean condition, i adjusted the mini-afc and it fixed it.