Jaguar Breather Stub
Checked the Breather Stub to comply with TSB 600-03 thinking this was related to my Restricted Performance issues. I found it to be as clean as the day the car was put on the street. However, if you are going to check it you need to be gentle with the flex tube and inspect it for any holes and cracks. If you do check the opening you need to be careful not to drop what ever you are checking it with into the valve cover. They recommend a 3/32 or 2.5mm, I used the plastic spray tip from a spay cleaner. It seemed to fit well without forcing it.
This is a link to TSB 600-03a
V8 XJ Series/XK
Part-Load Engine Breather - Partial Blockage