The number one cause of vapors inside the covers is a poor PCV system. Since you checked to make sure there is a strong vacumm signal from the PCV valve, make sure the breather on the opposite valve cover is not clogged up.

As posted above, run a 180 deg. t-stat.

I once had a pin hole in a water pump backing plate on a Ford and it allowed water to get into the oil pan and turned the oil into whiteish goo.