I got merc E 270 CDI, 2002 model, 180000km milage. Vehicle became sluggish particularly uphill, when you press gas revs do not go over 2000 although occasionaly things gets normal and vehicle is full of power. Went to Merc garage, they recommended to change injectors which are very costly. Friend of mine had similar problem and he said they change some electronic parts (air mass sensor). Any advise?