new car quest again? sorry

Hey folks I have noticed two noises of some potential concern and am just wondering if it is normal and my 2.0L GLS Jetta is just naturally breaking itself in? first one is this; I get a somewhat moderately audible clicking sound i.e. "click"-"click"---"click" for about the first few minutes of letting my Jetta warm up in the morning, usually I only hear this after it's been sitting all-night long at any other time it sounds normal???
My second question is kind of an odd one, say I drive my car conservatively as I usually do, on the freeway at tat for 20 min or so, by the time I get home and park my baby in the garage I always hear an loud hissing sound emitting from the driver-side rear wheel well, the sound is followed by small exploding like air pockets, imagine taking a plastic Ziploc® bag, closing it then popping it slowly? At any rate this goes on for about 5-10 min two days after I brought the car home from the dealer this went on for 30 min straight??? I have located the sound to be coming from the muffler, however I have never heared a hot muffler make any sort of noise like this before. If anyone can help me with both of these minor concerns it would be appreciated as I will be taking my car in on Monday for the humming noise coming from the front differential and would like to know if I should make them aware of these concerns as-well? Nonetheless I have just yet put 600mi on the Jet and am still ecstatic about it.

-Ryan
[Modified by MK4ryan, 3:15 AM 11-24-2001]


[Modified by MK4ryan, 3:18 AM 11-24-2001]