Slant 6 Turbo 68Dart Project

Of course I know very little but I'll go out on a limb and guess your gauge is not the problem. You're getting tiny boost and feeling it. When you get it sorted out, you'll know it and that grin will be from ear to ear.:burnout:

Probably true. But the fact that the gauge has a vacuum side, and boost side, and will not read vacuum when attached to the manifold where a brake booster would be is odd to me.