I was throwing a code with my new IE catted downpipe. I decided to try to space out the o2 sensor. I guess I got lucky with my first try, because after a reset and over 100 miles and 5 cycles I have not gotten the CEL back. I had a bank 1 catalyst efficiency below threshold. I used a Dorman 42009 and bored out the center to the bottom of the hole but did not go all the way through the end.