valve stems are cheap but a pain in the ass. If you have some spare time I recommend you do them so your more familiar with the car and how the motor works and have a mechanic check it out afterwards. I did that with my car, its just time and patience.
It can be a number of things, valve stems seem to be the culprit but Id check the seals anyway and replace the headgasket since youll likely remove the heads anyway.
My .02.
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Plato, Apology
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