excellent walkthough on valve lash adjustment took my truck to school and had some people look at it that was the first thing they suggested i do but most of them thought its a valve near the passenger side rear going to have to take it in and have them help me look when I get back to school from military training. If I have to do a rebuild is there recommendations as far as what I should replace while I'm at it the truck has 180k seems to run fine and gets between 22-26 mpg on my 50 mile drive to school with a mix of highway/city traffic into denver as far as I know the truck is stock but im sure it used to have an aftermarket air intake and programmer it has a BD exhaust manifold that looks new.