Sounds like the PCV is blowing oil down to the intake manifold - happens from time to time even in well running engines. Unless you have a flex-wand that you attached some cotton gauge material or similar to soak up the oil without leaving too much lint or other material behind, I'd just leave it. Will eventually evaporate in time - or if you feel adventurous and want to remove the intake manifold.
In the mean time, I'd look into making or purchasing an oil catch can. Even in a well running engine, there will be cases where some oil will get pulled through via blow-by. Normally, it is just fumes that will be burned off with the incoming air charge - but it can be quite oil laden. An oil catch can will help hold these fumes, condense the mix, and pull liquid oil out before it hits the intake system. Same principle as the oil and water separators in air compressor systems.
Some have reported better fuel economy in heavy contamination cases - though your mileage may vary. Some even used those translucent fuel filters as temporary oil catch cans - you can see the level of oil being trapped in them, toss them when they get too full.