Post a picture of the area you are talking about (oil leak). Crank case oil vapors are routed back into the intake via PCV lines. They would look like vacuum lines. I don't know much about the 5.0L to say if that could be the cause.

 

Here is a generic pic I have marked up. Oil vapour rebreather - I am familiar with this on other engines, so you could be right. Still not sure if that is what this is - it doesn't really look like it would do anything. I thought it might be some sort of induction resonance chamber!

 

It's not the PCV. You are right those are added to reduce intake resonance. I have them on my SC 4.2L. It's unlikely oil would be in that area. Say you had some oiled air filters in the system it could get in the intake tract but I'd highly doubt you'd see a leak around that area. Keep and eye on it but oil dropping on it from above is more likely. Do the hood vents happen to sit over those spots?