Black scum in intake manifold. what 2 do?

I was getting my oil changed today (yea, I know. do it yourself), and the mechanic guy took my intake off and was checking the TB and IM. he showed my this black soot/oil that was on his fingers after feeling around in the IM, and suggested that they do a fuel flush clean thing.
Do these conditions sound firmiliar? I’ve used and injector cleaner 10,000km ago. The black stuff didn’t seen to come from the TB, so I’m not sure if TB cleaner would do anything.

Suggestions?

I had a lot of black sticky goo in my TB, so I just pulled off the TB and scrubbed it out. It had been causing my throttle butterfly to stick close occasionally. I’m not sure what causes it, but it wasn’t hard to clean off, I just used some damp paper towels. Not sure how you prevent it.

ok, but my grime seems to be after the TB.