Yeah, by "pegged" I meant all the way to the left, or full vacuum.
There is actually a little post, or peg there for the needle to hit.
We are comparing that guage with a hand-held shop guage connected to one of the vacuum ports.

This came from and old term, when we would try to "peg" the speedometer on '57 Chevys.
Another bit or trivia: the seemingly crude term "balls to the wall" is actually a term from WWll. It means to push the throttles on a B17 all the way forward to the firewall. The throttles had handles or balls on them. Thus the term for "full throttle" became "balls to the wall".

Hitman, a couple of comments:
I asume you are working on the 300SE.
You mentioned pre-cats. Mine has little bulges on the pipes just below the exhaust manifod, they look like pre-cats. However, upon inspection when I had the pipe off one day, they are not; they are straight thru. They look kinda like an old glasspack, with little holes in the pipe to let exhaust circulate into the outer chamber. Must be a sound damper device.
If you have a calif car, maybe your is different.

Also, check the vacuum line 3-way T, that sits forward of the brake booster, and feeds vacuum to the climate control. I used little squeeze clamps to sung it up.

DG