if the plug was real wet i would change it first thing, if its not check all your head bolts again. like LT said a loose head will make a poppeing noise and cause it to run sh*tty. when my head studs sent bad i could look where the head and cylinder meet and see the oily residue. if all that is good your gonna have to pull the head off and get a good look at whats going on. is your TORS still attached? that can cause ALL KINDS of problems. what kind of oil you running?