I wish I could post from my iphone to this site. it sure would make this part easy.

What is the piece on the engine that is at the front Passenger side of the motor. It is round, flat topped about the size of a baseball. Positioned just below the valve cover. Slotted adjustment at the top?

 

Has a small window on it? if so, that's the cam position sensor.

 

Ok. I see that it is adjustable, by the slot at the top. Any performance gains to be had by adjusting it? I'm thinking like setting the timing adjustment?

 

https://www.jaguarforums.com/forum/x...engines-66536/

This is the only performance adjustment that can easily be made. It adjusts the timing.