I am having a reoccuring problem with my F-7 EFI. It started lst night when I was driving it and then it went down to one cylinder. I put 2 new plugs in and it ran fine for about 10 minutes then dropped to one cylinder again. Put 2 more plugs in and again it fouled out the same plug. Where would I start on this issue? After pulling the plugs out they look fine, but it still keeps fouling the same plug out.