Update: The CEL came on the next morning when immediately upon starting my car. I'm not sure why it's not working, I did everything correct. But it sounds like the things to check are, 1) Is there a exhaust leak 2) Was the hole drilled big enough. It did feel like I had to really cram the sensor in the non-fouler to get the threads to connect. Could this be the problem? Not enough room in the non-fouler? Thanks.