Hi everyone, I'm new here and I would appreciate some thoughts on my Mustang GT issue. I have a 2008 with the 4.6, 57,000 miles. I still have factory warranty (preowned but Ford certified) as well as an extended warranty thru another company. I have had no issues with her since I bought her nearly 3 years ago. Last night my CEL came on, and after running to AutoZone I found it was a P0420. My understanding is this can be several things. Ford dealer has it now and are replacing cats, they say that both cats come together. My worry is that whatever caused the cat(s) to go bad/melt/etc will not be fixed and I will kill another cat soon. It is not running rough, absolutely no warning signals until CEL came on. Anyone else have this issue? Its too new with too few miles to start having problems!