320 turbodiesel, intake fuems question

Hello ppl.

I own a 2001 bmw 320 turbodiesel 4-cyls.
Some days ago i saw some oil drops being on the waters rubber pipe under the metal pipe after the intercooler. (the engine now have 100.000 klm)
I removed the metal pipe from the engines intake to see what is going on and i found out that the metal pipe have a lot of coal inside the pipe.
Is this normal because it is a diesiel engine? or there is some problem?
When i step on the gas without moving the car there is no black or dirt smoke from the exchaust.
I think that this can happend from the fumes which goes from the engine headcap at the turbo way in.
If somebody have noticed the same thing please let me know.