I have the factory dual cats on and the pieces inside the are breaking apart and making a rattling sound. Undecided if I'm going to replace them or just have them emptied out. But in the meantime is it safe to drive the car with this problem or should I park it until I get it fixed? Thanks

 

Well I don't think your going to do any more harm to the cats they sound like they are already shot.

The problem you might run into is these pieces in the cats restricting airflow so much that the pressure will build in the exhaust causing your car to run poorly, and if bad enough it may get to the point where it is no longer drivable.

 

Shouldn't do any harm, just won't be as eco friendly as it used to.