You most likely need a set of spark plugs. The early design plugs are terrible and the gap widens very fast. I have pulled plugs with only 60k on them and the gap was over 0.070". The Motorcraft SP 515 plug is a lot better design and should solve your problems. The life of the coils will be shortened with worn plugs because it takes a lot more voltage to jump the gap and the spark duration will be shorter.