I'm surprised no one has mentioned that oil in the intake is lowering your effective octane rating for the air / fuel mixture. That is the main reason to run a catch can or breather.
This is not my writeup, but Jimmy did a great job here. I have a system identical to this. (Boss Ch. 11) Underhood mods Â« jimmypribble.com/blog
Works well as you can see, LOL.