Why is the DISA valve opening so gritty/oily?

[stamas]

my car: 2001 X5 3.0i

I recently had to remove a bunch of stuff from the intake manifold side of my engine in order to get at the pcv valve and pipes which I was replacing.

Along the way, I also cleaned all of the grit, grime, and shellac from the following items... all were really crudded up (160K or so miles on the car).
- throttle body... cleaned off grime and shellac
- idle control valve... now internal mechanism moves freely
- disa valve... this was recently replaced and was already getting gunked up.

My question:
Why is the internal area where the DISA valve is mounted so oily and grimey? Where does this grit and grime come from? Is this normal?

In the photo underneath the DISA valve opening, you can see the intake manifold opening for the throttle body... that area is clean and dry.

[bastereo]

It comes from the PCV/breather system.