wideband sensors provide a linear reading while narrowband sensors jump all over the place. So with a a/f gauge hooked up to a narrowband you are just going to get lights jumping back and forth from rich to lean.
If you want a more accurate indication of your a/f ratio you can spend $300+ and get a wideband system or you can send you gauge to someone that will chage the voltage your gauge responds too for a more accurate reading. I don't remember the place off the top of my head but i will search for it
here is how they work if you want to know
edit:
Thread covering A/F guages 
