Annoying noise in the brake pedal
 

Guys,
I'm a fresh enough owner of a 2008 model type Cayenne 3.6 Tiptronic and I'm experiencing a quite annoying noise when I release the brake pedal. It hit its stop with a certain violence and the noise is quite high... also because of the play in its structure.
Of course I owned tenths of cars so far and I usually rent many cars per year, when traveling abroad ...but I never experienced something like that at all...
You can also shake the pedal by hand and you have no doubt it's pretty noisy.
I bought the car at an official Dealer with a full warranty... but they say the noise is "standard"! I can't honestly believe it...
Does anybody know something about it and can help me?
Porsche, where are you?
Thank you.