Had a vacuum leak for probably most of a year now, just gave me a check engine light about a week ago for bank 1 too lean. Have replaced a few vacuum lines with no avail, but could hear a leak around where the PCV connects to the manifold so started to suspect a stuck valve. Got an aftermarket one from O'Reillys...doesn't fit. Looks identical to the Motorcraft one in the car but only goes in about half as far as it should and therefore doesn't screw in (this an '02 with the screw type valve). Return it and look on Ford parts and they got one for almost twice the money as O'Reilly wanted for the motorcraft one except O'Reilly can't order it anymore. Part shows up at the dealer today and guess what.... doesn't fit. Goes in half way and that's it. Tried taking a pliers and seeing if can make it go anymore and it won't, just tries to back out. But I have confirmed it's the problem because with it in as far as I get it, fuel trims almost make a full correction, will end up with about +5 but that could also be from it not going in all the way. Part number on the new one is EV-262 (YS4Z-6A666-AC on line below). Nothing really on the old one to identify it, got what I think is a patent number (PBT-6F30, then on the end that goes into the engine says M536M which is also on the new one. As far as I can tell they look absolutely identical but evidently something isn't right. Old one goes in and out easy and no damage. Old one is left, new is right (I chewed up the plastic a bit on the new one with the pliers) If these don't show as images in the post, right click the broken image icon and chose open image [in new tab], that worked in post preview anyways. Anyone else have a similar issue before? Did a quick search and couldn't find any relevant posts. Going to junk yard tomorrow to see if any of the cars they got have a valve and if they're the same.