i have a 99 explorer 4.0 overhead valve v6 thats running rough. check engine light is on & the code i pulled was mise fire on the #3 cylinder. I've changed the plugs with motorcraft platnums about 7 months ago & beacuse it was runnig lean in bank two. everyone on the forum told me to change the intake manifold gasket so i did & that problem was solved. but now its starting all over again but instead of runnig lean it has a misfire. please help me figure this out im getting really frustrated with this truck.

 

change the plug and or wire you never know sometimes could have a small crack in plug if it is only misfiring on that cyclinder.