I have no idea what was in the other thread you referred to.
Are you sure you don't have solid lifters/cam?
If you adjusted hydraulics to 1/2 or even a full turn past zero lash, you should not have that big a change in vacuum when you backed them out to zero lash.
If you adjusted solids as hydraulics, then the vacuum would go to hell real easy at anything below zero.
Several months ago I had a thread about this motor. It's gone with everything else. A bunch of folks including Larry, Frenchtown flyer and others had made posts. there were some cam recommendations in the original thread also but they are gone now and I didn't copy the specs...
Definitely hydraulic lifters....had some out. Vacuum increases (and idle improves) as lifter adjustment is BACKED off...thereby decreasing valve lift/duration but making the lifters rattle.
