With a Pentastar and even number codes you would be looking for the factory to replace the head (Chrysler had an issue with 3.6 Pentastrs in 11-13 models). In the XF I'd look to poor gasoline first with a P300 and ignition if confined to a specific cyl (e.g. P302). Can also be a failing injector since what the computer is looking for is a decrease in rpm when one or more cyl are supposed to fire.