I finally took my 98 E0 to the dealer for the rattling cat conv. It was so bad, I couldn't get past 3k rpms! So the dealer installed front AND back exhaust mainfolds and a new cat!!! It sounds and performs better than when I got it last year! I am sooooo happy. It would've cost 1500 bucks but it was covered, yay! I even got a rental for the day.
So anyone out ther that may even think they may have a catalytic problem, take it in. By the way, I only have 48k on the odometer.