I'm having the same problem with my 98 e320. After the car is warm, in gear and with foot on the brake (like at a drive through window) the rattle resonates off the side of the building. It sounds terrible. I think some stuff must break loose in the cats. (Damn those things). It's obscene that a car of this supposed quality has this kind of problem. I have 104K, so I'm out of warranty too. I'm going to my independent mechanic for his opinion this week. Maybe I can share some more favorable news with you by the middle of next week. In the meantime, if you hear of a fix, please post it. (I've thought about cutting the cats and/or the muffler(s) open, shaking out the loose crap, and having them rewelded closed). Fastlane-cats-$560 (x2), muffler, $470. Ouch!

Dave M