Well if it is a vlv issue you can get a compression kit fairly cheap to verify if you do in fact have a valve or piston ring issue. Of course this still does nothing toward the fix other than point you in the right direction. How mechanically inclined are you? Reason I ask is, I've never done heads either and I did mine myself. I made a few mistakes which cost me an extra $100 in gaskets and 3-4 hours of extra work but it runs better now than it has in a few years.

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2000, 4x4, 4.0 Ext cab