About the outside air being used as reference by 02 sensors, the wiki has this information too, which is odd to me. I always used to think the sensor is using some section of it that is to outside as reference air. This says it gets that reference air all the way from the other end of the cables. Don't know. All I know for sure is, when I fixed my leaking exhaust flange, my 02 code was gone:
"In automotive applications the titania sensor, unlike the zirconia sensor, does not require a reference sample of atmospheric air to operate properly. This makes the sensor assembly easier to design against water contamination. While most automotive sensors are submersible, zirconia-based sensors require a very small supply of reference air from the atmosphere. In theory, the sensor wire harness and connector are sealed. Air that leaches through the wire harness to the sensor is assumed to come from an open point in the harness – usually the ECU, which is housed in an enclosed space like the trunk or vehicle interior."
https://en.wikipedia.org/wiki/Oxygen_sensor