Oil getting in the intake is a reason why alot of people will not run a K&N cleaner. Others swear by the K&N, and say it is due to "over-oiling" so its all personal opinion.
That is probably all your oil is, and I wouldnt be alarmed by it.
I had the same situation, when I ran a K&N. Even though it was oiled from the factory, upon checking the blades, they were covered w/ oil & grit. Immediately got a paper filter, cleaned the blades w/ q-tips & brake cleaner, and havent had oil on them since.
In reference to your other post about warantee being almost up. It sounds like you have been fortunate, you got a good truck. Also, have probably treated it well.
Just make sure you have a fuel pressure gauge, and another lift pump handy, as yours will be coming due sometime. In fact lift pumps fail like belts & hoses, so you might want to upgrade to a better pump now, and keep the stock one in place as a backup in the field. Or replace it now in a comfortable setting, vs having to do it in the field.
I upgraded pumps before mine failed, so that it is still available in case the upgraded one quits.