My car, XJ6 Diesel 2007 which has 94,000 on the clock, has suddenly developed serious vibration through the car, as though the engine is about to cut out. It does not cut out and when stationary the engine sounds sweet as a nut when revved. No engine warning lights appear. The DPF advisory light has been on and I have done the usual fast run for it to extinguish. Believing the vibration may be being caused by a full filter I have now added a DPF cleaner to my fuel. Has anyone else experienced similar vibration?