Like I mentioned before, I'm currently running a Bob's Auto Sports catch can on my 5.0. Out of curiosity, I went out and pulled the quick connect off of the intake manifold barb. It's been about 1,300 miles since I last checked for signs of oil. Like before, there was a very slight film of oil on the outside of the manifold barb but it didn't discolor the Q-tip I used on it. I then ran the Q-tip around the inside walls of the barb and only came up with a very slight discoloration. I than ran a new Q-tip around the inside of the quick connect and I did get some oil colored discoloration but it wasn't really that much and the Q-tip was still mostly white. It was more than what I got from running a Q-tip over the inside and outside of the manifold barb.
It doesn't appear that very much oil is getting through so it seems that the Bob's can is doing it's job pretty well.
I plan on reinstalling the UPR can with the new diffuser at some point soon and see how well it does in comparison.