I have a '94 300ci 4.9l inline 6. Itsa good strong towing truck but i the converter rattles like pop cans. I checked to see if it was the heat shield, but it wasn't rattling. I took the truck to crappy tire and the mechanic said that it was the baffles from inside the converter and the noise should stop eventually. Its been gettin worse, and at red lights everyone looks around to see where the noise is comin from. Im thinkin of just puttin a straight pipe, and trashin the converter, but if I ever sell the tuck, it will never pass the safety. Another thing- when i step on the gas from idling, it will make an initial sound (sounds like an inhaler)
before it starts accelerating. I think it might be the air pump. Does anyone know whats going on? Thanks

 

Sounds like the cat. is just about plugged.
Don't get caught with a bypass pipe where the converter belongs, I understand the fines are hefty.
You may want to consider an aftermarket, hi-flow cat.
AL.