Engine light is on, ran codes, came back with many codes: 1399:probable blocked EGR, valve clearance out of range
P0300 Cylinder misfire; fuel system concern, ignition system concern, MAF sensor faulty,O2 sensor/air fuel ratio fault, blocked intake
P0302, 303, 304; cylinder misfire probable cause...vacuum leak, ignition system concern, blocked fuel injector, engine machainical condition
Where do I start> I was thinking EGR valve, but cannot find details on where it is/how to replace. Any help appreciated.