I'm sure this has been discussed and covered but I can't get the search to work for some reason. I have a 2001 540iT purchased about 3 months ago. Previous owner had replaced cats with ones from eastern Catalytic. They have maybe 6k miles on them. Started getting a really bad rattle on cold start a few weeks ago. Narrowed it down to coming from right side exhaust, thought it might be a heat shield. This morning rattle got really bad on startup (it was in the low 30's here in MD today) and then went away. This evening while working on car in garage, it stumbled a little, then spit a large piece of honeycomb out muffler.

My question is this - has anyone ever tried to get Eastern to warranty a cat ?? previous owner is looking for receipt and it is supposed to have a 3yr/50k warranty. or would it be easier and cheaper and better in the long run to go to a different aftermarket cat ? If so, which ones work the best and best place to get them ?

thanks !!