I have a RD28T patrol wagon (1998) and recently I have noticed a strange noise coming from the engine, it only appears around 2k revolutions and above which leads me to believe that it is the turbo, the noise sounds like friction off something rubber, as if something was dragging along a treadmill. I checked the pipes connected to the intercooler and they have oil coating them; I did some reading and it seems that the oil is normal without a catch can (which I do not have), I am not sure if that has anything to do with the problem. I am not noticing any power loss or any other issues other than the annoying noise, any ideas on what it could be? Any help is greatly appreciated.