dvt

looking for some advice/suggestions, i have a 2006 2.0 x type diesel, running fine until about a couple of hours ago, driving on the road at approx 40mph when there was a light psst noise and the car started to missfire, runs ok on low revs but acceleration very poor, and missfires when accelerating, no smoke no overheating and no warning lights on, starts on the button, but runs like a bag a bolts when trying for higher revs, any help would be appreciated