Hard (power) brake pedal

Okay. After some exhaust issues with the head pipe flange leaking I'm back to the brakes.

This is drum/drum. The check valve seems okay.
"engine off, evacuate the booster by pumping the pedal about 5 times. ..... If still no drop, relax and shut it off."

That's what I got.

Won't have a partner to help until tomorrow.

Here's a picture of the booster.