So - my shop has replaced my cat 2x and i still have the rattle - it seems the dealer wont be an option for me - 2006 w/93k miles. i am looking into custom options - that will keep torque. i will ultimately place an amg srt in the car. i need suggestions ASAP.

 

do u have a clamp (like a worm type clamp ) touching any exhaust pipe or maybe a loose heat shield that hits the engine on acceleration

 

Nope, already checked all shields and clamps. I am checking with the stealer, my friend mentioned there was an exchange program for cats because they had a rattler problem. But the shop I use has replaced it 2x - the second under warranty - when its fresh and new it runs like a champ. i wonder if it gets clogged and causes back pressure?