Doesn't sound good, PCV is a definate possibility. However, How many k's has your engine done? How often has it copped 18psi for? And lastly, how often do you change your oil? If you answer high, lots & not as often as I should, then rings are the most likely culprit. I'd recommend keeping the boost down, as high positive crankcase pressures are going to push oil into your intake, & then it will burn oil!!!!!