Intermitent Brake pedal feel
Not a hot rod, but while looking for a solution this problem is getting worse. 2000 chevy 3500 Express (van) just over the 100,000 mile mark.
For the first 97,000 miles had no brake problems. Had a definite feel of how the pedal normally is. One day instead of the pedal going about 1/3 way down to stop, I hardly touch it and the fronts lock up in the stones. The pedal is high, has almost no travel. It went away and the pedal and brakes seem normal again. Over and over at no apparent time, speed, or temperature, just a little touch of the pedal results in very hard braking. Sometimes (at a stop) pressing it harder, the pedal will suddenly drop to where it normally should be and the brakes work great. When pressing hard on the pedal and it drops, you can hear a weird noise that I can't quite describe. Somewhere online I had found the same symptoms and it said it was the hydro boost (I can't find the website again). I replaced the hydro boost. It still did the same thing. I replaced the hydro boost again, along with the master cylinder and the problem still persists.
It's not so bad having a high pedal that is very sensitive, but when you never know when it's going to suddenly drop a couple inches and act "normal" is the scary part.
Young enough to learn ... too old to remember.