I found this thread over on one of the other Jaguar forums and am now wondering if there is an underlying issue with the timing components of the 5.0L engine. The gentleman in this thread ( Restricted Power Warning Light ) had his timing chain and tensioners go due to supposedly running a 5w-30 oil instead of the recommended 5w-20.

Worth a read.

 

While I cannot verify that the tensioners are different. I will say that at my dealer will inspect the chain tension on a 5L Rand Rover and not feel that they have to on a Jag 5L. Also, a Jasguar 5L non supercharged engine's heads and cams are quite different from the 5L supercharged. That being said, some x351 owners may find that the "same" part for a Land Rover is cheaper than the Jaguar version. These parts are not the same and are built for different duty. Just my humble opinion.