My vehicle keeps mis-firing and check engine light on camshaft Sensor code

What is your question?

2004 Cadillac SRX V8- check engine light on and misfires continually at Idle, hesitates on acceleration and jerks when manual transmision shifts at low speeds. I changed spark plugs and all 4 Camshaft Position Sensors sense that code and code P0300 was detected but car still does the same thing after the change. Also now I have a rotten egg smell from exhaust pipe which the Catylitic Converter may have failed. What can be causing the misfire? I understand that it would make no sense replacing the cats until the misfire has been corrected.