I had the same exact problem with my 06. I thought the cat was bad but it just ended up being a faulty 02 sensor. Check the voltage of all 4 sensors using a scan tool to find the culprit, replace, reset the MIL and you should be all good to go.Got a P0420 code, check engine light is on. Relates to cat below efficiency threshold. Thinking bad resonator between cat and muffler, sounds and smells bad. Anyone with similar issues?