Proper operation on a narrow band is different than a wideband. The output valves are different etc.
Narrow band reports in millivolts between 0 and 1. It should always be fluctuating from low to high or say 200 to 700 to 150 to 800. The faster it flips, the better. A lethargic sensor is on it'* way out, and causing excessive fuel consumption. At rest or unplugged a NB o2 should read 450mV.
Wideband sensor reports from 0 to 5 volts and/or in Air Fuel Ratio (AFR). AFR is important and under normal cruising our pcm aims to maintain 14.7 AFR. This reading only fluctuates by the true AFR and does not bounce up and down from lean to rich like a NB.
00 Regal GS: All kinds of cool stuff.