[Jeff Chambers]

Be aware though that in running a breather on an EFI car will result in lean conditions at idle and part throttle. Anytime you're under manifold vacuum conditions, air will be sucked in through the breather, passed through the PCV and ingested by the cylinders. This is air that has not been metered by the MAF so the engine will run lean. Most times that I've got a customer complaining about idle surge/hunt, its because they've put a breather on the car without understanding why Ford had it designed as a closed system.