So my CEL have been going on and off the last week, and sometimes it sounds like marbles rattling around when I'm idling at the stop light. I read that it might be bad catalytic converters, so I took the car to the dealership for diagnosis.

They have confirmed both catalytic converters are bad and will cover all repair expenses. I am so relieved. Luckily I brought it in now cause I'm at 79,200 miles. If it failed after 80,000 miles, I would have been SOL.

Mine's a 2007 4.8i. Just putting this information out there, just in case others are in my shoes.