If you got a sensor that hooks into your stock O2 sensors, they're about useless except to "guestimate" your A/F at wide open throttle. I don't know what color wire it is, but if you watch the guage, and it goes to mid-way or so (aka: stoichiometric point) when going down the road, and swings up to that point and back down often, then you're OK... The only indicator that really matters is what it does when you go to wide-open-throttle... If it doesn't swing to the rich side at WOT (aka: 70%+ throttle), then you want to richen up the car... That's about all they will tell you... It's normal for them to show nothing on the guage when the car is near idle speed or when the O2 sensors haven't heated up yet...
The reason the readings are so eratic is that your ECU controls A/F ratio at anything below WOT for fuel economy/emissions reasons. The only thing that meter will show you driving down the road at cruising RPMs is a pretty blinking light... It gets quite annoying after a while... When you hammer it, the ECU stops trying to achieve a stoichiometric ratio and goes to an open-loop configuration where it doesn't monitor O2 sensor feedback to determine A/F ratio...
