I'm having trouble with a small misfire. I have used Autolite plugs and they weren't worth anything. The Motorcraft platinums started the mis fire, I changd them to NGK platinums and the mis went away, but after a short while, I developed a leak, fixed that, then put in some Bosche platinum 2 plugs and the mis is hardly noticeable, but its there. Can anyone help me?