Dirty inside intake manifold behind cold start valve. What to do?

[scoot]

I'm working on cleaning the fuel system on my W112.115  M189 engine -- almost ready to try to start it.  Currently removed CSV for inspection and cleaning and replacement of the two rubber O-rings.  All that's fine and I have a good spray pattern.  However looking inside the manifold it looks pretty awful.  It's black and sooty looking.  It isn't wet.  A dry paper towel wiped on it through the CSV comes out looking kind of black.  If I spray a little carb cleaner in there and wipe it comes out with more crud.

Is this normal?  I'm not removing the intake manifold for cleaning.  Questions:

1.  Is this normal?
2.  Does it matter?
3.  Should I clean what I can reach?

thanks
Scott

[scoot]

FWIW I just removed an injector and it was really dirty in the same way as the inside of the manifold...  It's soaking in diesel at the moment...