For some reason my XJR will not keep the brake booster vacuum line alive in this car. The Y junction kept snapping. Between 75k and 78k I went through 3 of them. Though they were used EBay lines, I got tired of spending $60 on a simple system that kept breaking for unknown reasons. I built my own line out of very thick walled silicone tubing using the factory connectors. This allowed me to tuck the lines a bit more out of the was from hot areas and gave me a system that had some flex and vibration resistance beyond the rigid plastic that Jaguar used.

If your car has this problem - you can easily replace with you own system with something that in my opinion is vastly improved.