Originally Posted by fos160se

It sound that nobody realy knows whats going on. Lets do some "research" on the problem. If the car is friven in stop&go traffic eg. peak hour traffic the brakes become hard to press, so in stop&go traffic the engine don't realy get the revs up - Now lets do a simple test with a car thats got no brake problems , after driving the car switch the engine off and press on the brake pedal several times don't the brakes become harder as in this case(problem reported)?
The only reson for the brake pedal to become harder is the lack of vacuum when the engine is switch off and if my teory is corect if I'm saying our friend with the "hard" brake pedal got a vacuum leack someware between the brake booster and the engine.
That is why in stop&go traffic the brake pedal becomes hard and when the car gets driven in a normal way the brake pedal feels beter(softer , normal). The problem will get worse with the vacuum leak becoming worse.

So check for a vacuum leak in the brake / booster system.

Hope this will help anybody that gets this problem.