I just spent two hours trying to find where the noise is coming from. On both exhaust pipes on my 2002 E320 4matic wagon 34,000 miles, there are small cat converters? or resonators or mufflers the size of a softballs. When I hit the passenger side one(it has a flex, bellows looking section) with my fist it makes a noise like something heavy is inside. I loosened all the clamps and fastners thinking I could adjust and stop the noise, but no help. Am I stuck and do I have to take it to a MD dealer? I read that cat converters are warrentied for 8 years with a transferrable warrenty. Is that true? Thanks in advance, John.