I have a very slightly used Catalytic Converter for sale. This is an aftermarket unit that I bought from Ecklers several years ago in an effort to get my car to pass a Georgia emissions test, which it failed.  This is a Catalytic Converter that does not connect to the Emission system and it has probably less than 100 miles driven on it.  Since then, I replaced the entire exhaust system and disconnected the computer command system (A.I.R., etc) because now that the car is 25+ years old, it no longer requires an emission inspection.