When I was replacing my TB, I saw oil residue all on the inside of my intake pipe, down the throat of the stock TB, all over the butterfly, and down into the intake runner. I just went and bought a cheesey little APC filter, resprayed the little cap gloss black, got a piece of rubber hose to go from the valve cover to the filter, and plugged off the port on the intake.
If that was good or bad, I'm not really sure. But, I haven't had any performance problems that I know of, and I just like the fact that I don't have oil down my intake anymore.