its really hard to actually define what it could be cause i can not hear the noise for myself but i would start by fixing what you KNOW is wrong with it , and put new coil packs on it , or when you take the plug wires off just see if they are rusty . but if none of that works i would say try to get your vavles adjusted . and gl doing those plugs . everytime i did mine it was on a lift . so much easier that way .