Audi A6

Hi All,
I am new to this site and as you can see, I need some help if figuring out my problem. I have a 2003 Audi A6 2.7T. I bought it with 36,000 miles on it. I have driven it on the highway for about 1200 miles so far.
Recently I hear this rattling noise coming from the front end of the car, underneath and it is only there when the engine is running. When I switch the engine off the noise stops. The rattling is there when I am not moving and parked with the engine running. Any help on what this can be?
Also, secondly, when I am in traffic and I have the brake pedal lightly pressed I hear a scraping noise and a knock in between also. This does not happen when the bake is firmly pressed.
Both these problems usually start after I have been driving the car for a little bit.
Please let me know anything that might help me figure the issue out. I have the car still under the dealer warrenty for another 2 months and would like to get it fixed before that.
July 10, 2007.

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