I have a 99 Audi A4 1.8T quattro (tiptronic). It just hit 100k yesterday. The last few days I've noticed that when I start the car, I see bluish smoke billowing out the exhaust for about 15-20 seconds then dissipates. It only seems to happen when I start the car after the car has been sitting for at least an hour. It does not do it every time, even when it hasnt been driven in a while. Anyone have any ideas?