valvetrain noise 5.9 magnum

I threw my vaccum gauge on the engine yesterday and it makes 18 hg of vaccum at idle and the vaccum is rock solid steady. I have read if a valve is messed up that the vaccum will fluctuate at idle.
Vaccum is steady at idle. So should I start by taing the valve covers off and making sure all the rocker bolts are torqued to 25 ft lbs, is there a way to adjust the lash on these?