Has a random misfire Code P0300 catalytic convertor gets red hot .

03 Cavalier my random misfire pulled plugs and swapped no fix found it was coil which is one part held in by 4 bolts. Due to my time and cost changed coil and module and bulb or the rubber what we use to call plug wires. Have not torn down the coil yet but its an encased plastic part so any damage I find will be wast to describe. Parts replaced fixed random misfire.