I have a 2010 XF 3.0d portfolio and recently it has started to develop an intermittent issue where it the engine power drops away and feels like it will stall when pulling away from stationery. This happens for about half a second and then the power kicks it and everything is back to normal. There are no warning lights and under normal driving there is now loss of power. Also the power can fluctuate slightly when cursing at low revs. Any ideas?