had a constant misfire before
-changed plugs and misfire was gone except when engine is still cold. if i drive it when cold it has/had a rough idle and bogs down. im told this might be a manifold gasket vacum leak, gasket shrinks when cold and leaks.

-anyways, it threw a p1000 and p0307 cylinder 7 misfire CEL today just before i planned on working on it.
-measured the electrical reistance to all injectors on drivers side.
they were about 14.2, 17.8, 15.6, 15.2 starting from fr to back so i figured injectors were still good
- decided to check plug in cyl 7 even though just changed a month ago and found it came out nice n easy but was very very dirty on outside of ceramic, not quite soaked in oil but very dirty for only a month old.
-cleaned up plug, installed new cop i happen to still have but didnt use.
-reset codes and no codes on first test drive so far.

so i dont know if it still has rough idle on cold drive away till morning but does a dirty plug like that mean theres a leaky valve cover gasket or what is going on there?