can you put an air ratio gauge on a carb engine?

 

do you mean air to fuel ratio?

 

yea, can it be used with a carb? or only fuel injection?

 

It works with either one, cause it looks at what comes out of the exhaust. If you have a catalist the probe has to go before the catalist. You will have to weld bungs on the exhaust where you want to screw in the wide band O2 sensor.