As a thought did your lifters start to make noise in the mornings now too. I would watch the coolant reservior and make sure that it stays at the same level. Classic intake leaking into the valley you will not see any Dex cool in the oil as it evaps in the valley but things get alittle noisier in the morning and oil pressure does a slight drop - don't panic but take a look cause it could save you the motor. Colant system pressure test helps to ID.