PO420 even AFTER an o2 sensor simulator. Why do you torment me?!

[VibeHigher]

I have been struggling with the cursed PO420 code for well over a year now. Last time, I replaced the cat and it got better just long enough for me to get it inspected. Then it came back. I have tried everything, but finally decided to just get an o2 sensor simulator and be done with it.Or so I thought. The simulator is working correctly, I even have a video to prove it: http://www.youtube.com/watch?v=H1318eVbmokThat shows the pre-cat 02 sensor on top and the 02 simulator on bottom. Everything looks good, right? THEN WHY AM I STILL GETTING THE CEL??My only hypothesis right now is that the heater circuit for the 02 sensor isn't always on. The simulator relies on the 12V from the post-cat heater circuit to work. Once it's all heated up, does that circuit stop getting electricity?