nodoor - I'm not a mechanic but I'll give you some advice that may or may not help. There are many instances of 2006's developing a crack in the header manifold which results in your catalytics failing. Many guys on here have had this problem with their cats plugging up. This will set off codes for your emmisions - including your o2 sensors. Apparently just replacing your cats will not solve the problem long term because the comprimised headers will result in another cat failure and waste of good money. I suggest you look at the cats and also see if there is a exhaust leak or crack at the headers. You may not be able to see the crack if it is small and hidden under a tube - so you may want a professional inspection. My intuition in saying it would show a code 0420 was almost on mark. A 0420 is for the downstream sensor, where your code was for the upstream sensor. Pretty close in my opinion. Also - have you noticed your center console where the shifter is, especially the shifter bezel ring, is unusually hotter than normal? This could help confirm a leak in the headers as well.
