i have a misfire problem, engine light is throwing P0308, P0174, P0316 codes, 0174 is lean on bank 2, 0308 is misfire in 8 cylinder, but what the hell does P0316 mean, its an unknown code in my manual, so i put new plugs in it and changed the eighth cylinder coil pack and it still misses, someone told me it could be a burnt valve, is this true? my mods are K&N cold air and mac off road H pipe, any info on this subject would help, thanks