A shop in the Bay Area that specializes in Jaguar repairs quoted me $2,700 to replace the "passenger side valve cover and diaphragm." The diagnosis is that I have an air leak as well as an oil leak on that side, which soon might damage the alternator. Definitely true about the oil leak, which I noticed. Mechanic said for the XF, it is not easy to get to the valve cover (must remove the supercharger) and would take 9-10 hours of labor. Is this reasonable? I don't know anything about this type of repair.