Wow that's pretty clogged, Now I'll have to order a valley pan gasket for mine as well. I haven't taken one off, Chefro just did his he might know or auditech79 would know. I'll PM them and find out.

You may want to work on installing a catch can, it routes the vent lines into a canister where the carbon particles are filtered out and left in the can. You would have to read up on them because you need to design it for your own car. Then again that has most likely been building up since it was new so it may be another 100k before it would happen again.

 

I am making sure the dip stick tube isn't sealed until I can check if there is pressure building in the crank case. I saw a procedure, just need to find it.

If there is pressure building in the crank case under boost, I'll have to go into the spider hose, crank case vent and PVC check valves.

 

In the C4 I don't have that crankase ventilation valve. In the valley pan are two oil retention valves, which presumably must be replaced if the valvetrain sounds noisy on short drives, although the noise may go away on longer drives.
Since you said the intake manifold has to come off to get to it, the crankcase ventilation valve looks like something it probably sits on top of the valley pan, instead of the C4's simple cover. I would definitely remove it and clean it, versus replacing it. The gasket is pretty cheap ($ 4-6). You may need new manifold gaskets to the heads, though, if you choose to clean it and remove the manifold.
If you remove the manifold, you may consider cleaning the throttle body as well.