Hellow there i have a 88 stang lx. It had a issue not to long ago where it would hesitate and pop and wouldent whant 2 go over 3k.I try everything till i put new plugs it ran great and smoth by the way there motocraft.So the other day took the stang out and it stared with its spudering and hesitating so i pulled the plugs again and the plug 7# and 8# were preaty oily on the treads and on the tip. What causes this so now i guess i have to get new plugs the ones in the car now dont even have tree weeks. Ur guys help is greatful.