one of the cats on my 4.2 is making a ratling noise when ever i start the car. can i replaceone or should i do both? also does anyone have any part recommendations, thanks...

 

Audi covers their CATS under warranty for all pre-facelift cars. Get it fixed before 80k

 

would you happen to have any contact information?

 

I had same problem on my 2.8 V6.
That was catalitic converter broken from inside. I just went to my friend service to do somethink. He just "open" the converter an took out all from inside out. Then he just weld the hole. I need replace new converter before my inspection expired.