Just sharing this with the community to help other avoid my costly goose chase. Bought my 2000 XKR coupe a year ago and started getting P0400 -- "EGR flow malfunction" code after I drove it off the lot. Took it to Jaguar and they said the EGR valve needed to be replaced. Had it replaced as advised for $700 and the P0400 reappeared about 100 miles later. Did some of my own searching and found I was not the first to do this with the same result. The culprit is the Supercharger bypass accuator had a vacuum leak. Had that replaced and P0400 is gone!