Tinkerr.
Yes I have. After installing new MC and new distribution block, and rear flex hose. I took the car out and once again I had good working brakes until the car was up to temp then it went to hell. Brake pedal feels like it hits a wall near the bottom, brake light comes on, and very little braking.
Next day I put it on stands to experiment. Started car and had good booster, good pedal, no light. Checked vacuum at 15in idle (cold). Pushed pedal about 30 times while warming up and everything was good. As soon as car was to temp, the problem came back. However when I pushed the pedal and hit the wall of resistance about halfway down and the light comes on, if I help pressure on the pedal it would drop another inch and light would go off. I could repeat this over and over.
Somehow there is a pressure issue in the system but cannot determine where the issue is.