clogged cats sound very possible. with that misfire...sometimes gas escapes into the exhaust system during a misfire and when that cylinder finally does fire, it ignites the gas in the manifold and essentially "bakes" the brick in your cat. if you have little chunks of clay like material (hardened) in your tailpipe after driving, this is what it is. if not, i would most likely say clogged cats. take it to a mechanic if you cant gut it yourself.
