Hissing brake sound on '09

[s_c5519]

Truck has 2,000 miles on it, it's been doing it since I bought it. When I apply the brake there is a slight hissing sound coming from around the same area. It seems to go away if I press the brake 2 or 3 times or more immediately, but it does it every single time on the first press... Also I feel a tiny amount of feedback on the brake pedal when this sound happens...

Does anyone have an '09 and possibly an '08 and can check if yours does the same. I brought it to local Hummer dealer and 2 different people checked it out and said it was fine, that is normal, and they hear that on other different '09 vehicles. I forget what they said it was, but they said it was NOT a vacuum leak, which I was surprised to hear. I have had an '05 and an '07 and it definitely did not do it on those two, so I am guessing/hoping that is a normal thing on the newer H2's. The next closest Hummer service is about 50 miles away so I would rather not drive there for nothing too...