Once again.
The rotten egg odor is caused by lean to rich mixture fluxuations. The mixture is not being controlled enough to stay within the narrow range that it should. Bad catalytic convertors cannot make this smell, but the cause of this smell can kill the catalytic convertors.
An overheated or glowing catalytic convertor is getting raw gasoline from a missing cylinder or other causes, The gasoline is "burning" inside the catalytic convertor.
