Probably happens a lot more than we think. Thing is, these 2.5-3.0 diesel engines have a lot of ressources and are so enjoyable that they can somehow make up for minor issues such as leaking air, partially blocked DPF (until the DME restricts power at least) etc and keep a decent power output so that the driver still feels comfortable on the road. One day, after some work done on the AC compressor and belt, the turbo hose was put back in place and it made a huge difference, which made me realize the intercooler-to-EGR hose was actually dead. But I simply got used to it and the car still drove "fine" (I did notice higher fuel comsumption).have i been driving a sick car for 2 yrs without knowing it...
Have you already installed the exhaust pressure sensor ? As for the glow plug controller, check if it isn't covered in oil.