Snarling brake pedal

So, I’m proud Fox owner since May 2006 and unfortunately have the following problem since September 2006: My brake pedal knarrs sometimes when I want to brake with 80 and in the 5th gear. Not as strong as with an ABS brake, it is more a feeling that I press on air and give it gradually. It also a little bit but not very loudly, I notice this rather on the foot. Also you notice nothing else, so no big reeds in the car or something like that. I was already in the workshop (4 times the same) and had it looked at. The first time the fault memory was read off: nothing to see. The second time the vacuum hose would be renewed: also no change At the other two times only test drives were carried out, because this nice problem only happens once in a while, and the typical demonstration effect was there again. with the workshop master found out that I should apparently change my driving mode (he said that I should just slow down harder). I personally think this is stupid, because it doesn’t depend on the driving method, but simply that this problem is there at all. Also on the brake… Just wanted to get one (like many more) opinion(s) here, because I really don’t have any idea what to do anymore. As a woman I was dismissed in the workshop by because “she has no idea of cars anyway”. I just want to know possible causes for this problem… Would be great =)