Here's my idea/plan. I want to take a wideband air fuel monitor that has an analog aux output that's a 0-5 VDC siganl, 0V = 10:1 A/F ratio, 5V = 20:1 A/F ratio. I want to come up with a Comparator circuit that accurate to the .01V range that I can preset a trigger point so when the A/F ratio exceeds the set point it will trigger a mosfet or optoisolator that I'll have wired to set of injectors to richen the engine up. I'm an older guy, 50 years old just starting to learn working with electronics. My background is in Diesel Mechanics and Power generation. I have a good grasp on how things work. I tried building one with a LM-339 and could not get it to work at the lower voltage range. Somewhere along the way I think I "overloaded" the IC and smoked something, so I figured I'd ask someone that knew more about this than I. This is going on a carburated engine in a 1970 Buick electra 225 with a turbocharged engine.