Guys, is the factory rocker setup non-adjustable? I can't remember.

If it has stud mount rockers I would remove the valve cover on that side and back the stud nuts out a turn. If that didn't work I'd try another turn. If the nuts are adjusted in too far the valve may not close. Try comparing how much thread is above the rocker nuts to the head on the other ide.

Even if the cylinders are not firing, it should have compression. 150psi is decent compression. As long as the cylinders are all close to each other I would be happy. Compression guages always seem to read low for me.