You might be on the right track as a bum PCV valve will do exactly what you are describing.
White smoke associated with a blown head gasket and burning antifreeze is truly 'white' and behaves like steam when coming out of the exhaust pipe..it just disappears into thin air. Smoke from burning oil will have some faint blue tinge, but won't disappear like coolant smoke, it will hang in the air and trail for quite some time.
Stuart
