Hi. My 2010 Subaru Legacy TDI has developed a stutter at 1600-2000 rpm. It is better at operating temperature than cold. The stutters happen about twice a second, and vary a bit in strenght. At the worst, the whole car is jumping. This only happens when golding steady speed. It disappears at once when accelerating. Idle sounds fine, and car pulls fine. There is also a lot of blowing noise fron the turbo, and a warning light for the DPF has come and gone after some hard driving to rempve it. No other warning lights. Bad Egr-valves usually comes with warning lights, don't they? Faulty injectors? What could it be?