Took the car to the dealership and they told me it that it wasn't the catalytic converter but everything past it. They quoted me $1,800. 00 to repair and the extended warranty I had purchased from them wouldn't cover it. What the hell? They guy felt bad and told me that it wouldn't hurt to drive it, which we have for a few years now, but the rattle has gotten a lot worse and is extremely embarrasing, to say the least.