Like I said I am not familiar with Diesel engines. Sorry for my lack of part description. The tube that runs between the turbo and the right side of the engine if you were facing it. It has the word Turbo on it. It is very black. Not sure if its oil or exhaust residue. I think it runs from the turbo to the intake. My buddy said it probably comes from the cold side of the turbo. So more then likely the turbo is leaking in some way.
I'd give that engine a pressure wash, and then take it from there. Can't see much when there is so much crud built up in there. Then you can look for fresh oil leaks etc. Could just be something simple.
If you're referring to the vent that goes from the crankcase to the intake hose having oil in it then yes, it is normal. The crankcase will build pressure and oil vapor or mist will be transferred. My Subaru does it, my G8 does it, my VW TD does it and my HJ60 does it.
I use non vented catch cans on most of my vehicles. So it goes valve cover-catch can with stainless mesh- intake tube pre turbo.
I get small amount of oil out the cans on every car, every time.