Chevrolet Repair: 3 cylinder missfire on obd2, fuel injector, hi mike

Question
obd 2 says 303 code, missfire on number 3 cylinder.changed spark plugs and wires whats next besides cap and rotor.

Answer
HI MIKE,WHATS NEXT ?? GOT AN HOUR ??? SINCE I DO NOT KNOW WHAT ENGINE THIS IS I CAN ONLY ANSWER YOUR QUESTION. POSSIBLE PROBLEMS ARE,,, FUEL INJECTOR,BAD VALVES,BAD MODULE OR IGN COIL...IF YOU NEED MORE HELP I NEED TO KNOW WHAT THIS IS THAT YOU ARE WORKING ON,WHAT YOU HAVE OR HAVE NOT CHECKED. ALSO ARE YOU ABLE TO CK SPARK,COMPRESSION AND FUEL INJECTOR PULSE ???? LET ME KNOW...