Do not change anything until you check the rubber PCV elbow at the rear of the intake. As posted on here before it does go bad and since it is rubber the oil and vapors from the engine being sucked to the intake eventually deteriorate the rubber til it eventually fails. By the way I put a plastic elbow in place of the rubber but did order the rubber elbow only instead of the whole assembly which I think is what Ford sells. O'Reillys Auto Parts has the rubber elbow or can have next day delivery. Just posting so you check this before changing an expensive sensor first like I did. Duh huh......

 

Yep, I used a 90 degree spark plug boot on my Windstar and it works fine