With the car idling , outside in the fresh air , turn the valve on , on the propane torch , but do not light the torch . So that it is discharging a stream of propane vapor from the tip . Move the tip & the propane along and around all vacuum devices and hoses that you can find & get to .

If you stumble across a vacuum leak , the idea is the propane will be sucked into the engine and burned as a fuel , just like gasoline . This should cause the engine speed to increase .

The propane should not damage rubber or plastic . DO NOT do this while smoking . Be a good idea , the night before ( wait till it id really dark ) , to start the engine and raise the hood . Look for any arcing from distributor , coil or spark plug wires . You do not want to set the propane on fire !

I have gotten the idea that a cat is pretty expensive ? I have never purchased one . Did it look like it had melted down . An engine running rich is suppose to cause them to over heat , big time . Back firing may shatter the ceramic ?

When you get the cat replaced ( are you going to need gaskets? ) you can clear codes by going to your local chain store auto parts supply . Or , remove one battery cable from the battery for several minutes . Or , maybe by removing the fuse feeding the car's computer ?

God bless
Wyr

God bless
Wyr