I noticed that a lot of oil was coming into my throttle body from the vent tube on the passenger's valve cover. The air should be travelling in the other direction. Does anyone know how to test the health of the PCV valve?

 

Actual the system flows both ways depending on engine vacuum, gotta get rid of blowby at WOT too! The simple test is to remove the valve and give it a shake, if it rattles it's good. You can clean it out with some solvent. The valves are so cheap it wouldn't hurt to try a new either.