Hello Scotty,
Is it possible for a catalytic converter to break down internally without restricting the exhaust? My car won't pass emissions for several reasons, but the mechanic on-site told me the catalytic converter might not be doing its job even though it's not clogged or restricting the exhaust at all. It's a '78 Olds and we suspect the catalytic converter might even be the original one from 1978, so I'm going to be replacing it either way.

yes it can do that. when that old