I Have a 2000 Windstar 3.8 6cyl, I recently had a code P0507 which read engine running lean. I replaced the intake gasket along with a few other gaskets, no more code. My question now would be when my engine is idleing it hesitates sort of a misfire, also when I'm driving it feels as if it has a misfire. Does anyone have a clue as to what this may be? Mechanic says plugs are good.