[IceBox]

This usually happens when the car sits for awhile but can occur whenever you start it. When I went to buy my (used) Boxster, I almost walked away when a large cloud of smoke errupted from the back-end. I don't know which is funnier, my brother and I letting out a startled 'Whoaaa-aaaoooo' in unison or the panicked look on the salesman's face when he thought we were walking. He explained why this happens, but as I was satisfied with his explanation, and further research confirmed what he said, the particulars escape my memory. Suffice to say, no need to worry. Damp cold temps can also cause this...I don't know why.