hello,a mate and i just done the head on my xf and its all good except it runs rich i cleaned the carbon off the spark plugs just wanted to see what you guys think its is? im thinking fuel filter

can you explain a bit more about what you mean by running rich?

Make absolutely certain you have no vacuum leaks. These engines are shocking with the tiniest of leaks.
Mine turned out to be the EGR valve had crapped itself and was leaking.
Good thing I didn't listen to the mechanic and pay $250 for the injectors to be cleaned to fix my rough idle problem.

ok cool thanks ill check the vacuum lines and egr