I've never heard of manifold vac that high when checked, as noted below. Where are you connecting? I assume you know normal high side is 22".
The usual places are pure manifold accesses such as "full" vac side of carb base, PCV, or booster vac ports.
Hmmmm?
Thanks, I see it now. When I first looked for it and you indicated it was there, I didn't see for some reason. Oh well! That certainly looks like a good location to get a reading.
Good Luck!