There will be oil inside there to some degree. If it's excessive, you will want to clean it and def take a look at your PCV setup.
To clean it, i've used simple green on stiff wire brush that I can fit inside. Submerge in a tub of water and scrub away. I've been able to get the lower intake pretty clean inside like this, but the upper one you can only do so much for obvious reasons.
I'd just get it clean enough to the point there are no loose particles that can flake off. Obviously, make sure the upper is free of water before you reinstall.
To clean it, i've used simple green on stiff wire brush that I can fit inside. Submerge in a tub of water and scrub away. I've been able to get the lower intake pretty clean inside like this, but the upper one you can only do so much for obvious reasons.
I'd just get it clean enough to the point there are no loose particles that can flake off. Obviously, make sure the upper is free of water before you reinstall.