So, my totally stock 65 driving down the highway and brake pedal is rock hard when trying to stop. Check the usual, hose (good), check valve seemed okay. Upon further inspection check valve seemed bad (air would pass either way). So I order new check valve, get it and install thinking problem solved, but no such luck. Start car up after it's warmed up I step on the pedal and sadly it is extremely hard to press, and when I do push pedal, the car starts to run rough (vacuum leak). Long story short, could it be something other than the brake booster needs to be replaced. Never had to replace one so not sure if I'm overlooking something.