You might google on "automotive oxygen sensor" to see how the sensors work. As I understand it the sensor and companion circuitry produce a low voltage output that varies based on oxygen content. The range is limited as are the operating conditions (usually high temp). That voltage can be the input to a controller - the controller's output would be governed by the input from the sensor. You would presume that the controller's output would do something that would result in a change in the oxygen content. You might google on "proportional control" as a place to begin to understand control systems. I do not think that proportional control alone would be sufficient in this application.
Could it be a kit - probably. Reliability - uncertain and highly dependent on the builder/installer - among other things.