wideband problem

last night went for a ride whit the duster

at first I notive the wideband gage was gouffy ( autometer 4379 )

AutoMeter Ultra-Lite Digital Gauges 4379

but the engine was cold and didnt let the time at the senser to heat up
so didnt care much about it

after maybe 20 minute of highway driving a took a look at the gauge
and saw a 17.0 reading !!!!!!!!!!!

I know the carbs is ok and have the right jet in it
thats the carb I went to the dyno with so ...

playded with the gaz pedal a little to see if the reading change
it change but about 30 second later and ounce again with wird number

if I let the engine idle and play with gas its wird all cind of number showing up


whats wrong ?
do I need an other senser?
do I need to buy the autometer senser ?? pretty costly just for a senser !!!

thanks bob