I hadn't considered hydraulic. That may be what he meant. I have a slant and, yes, the FSM instructs you to adjust the valves hot and running. That may have been what caught my eye initially. If you alter the lash, the overlap will change, but the amount of vacuum will also depend on the timing. If the change in overlap moves the timing point to where the explosion is less efficient, the vacuum should drop to indicate this. Theoretically :-D.
Like I said, next time I adjust the valves, I'll see what happens a little this way or a little that way.
