I've had a rattle under my 97 TJ (2.5 engine) for over a week now, its driving me crazy. I got under the vehicle this evening with it idling and discovered the noise is coming from the catalytic converter, its not loose, the heat shroud on top of it is tight and is not causing the problem. The rattle is coming from inside of the converter, sounds just like a bolt or a nut bouncing around in there. Guess I'm going to take it to the local muffler shop and let them pull converter off and give it a good shaking to see whats causing this noise. Anyone else ever have this problem?