Seems that most of you are having this occurance during cold motor conditions. Forgive me at this time I do not have the date of build and some other information with me, I will post that for the sake of this discussion later on. I have the 2.5 engine in a 2002 TS. It is my belief that the smell is coming from the tailpipe as unburned fuel. Check yours the next time get, stop as soon as you can get out and walk back around the tailpipe. Do not stick your nose to the pipe but get down around it and you will probably notice the smell there. The car's computer will compensate for engine coolant temperature by allowing more fuel, this makes the engine run rich to keep it running when cold and get the coolant temperature up. From my observations that is all this smell is, and it has occured many times on my car. It also occured Sunday when I was teaching my Mother how to drive my car, it is a manual transmission and she has never driven one. Anyone who has taught someone to drive a manual knows what your car goes through, especially with the fluctuation of the accelerator.
In cold weather, the barometric pressure is generally low, this will keep that unburned fuel smell from the tailpipe down low, and allow you to smell it in the passenger cabin. How does it get in there on a cold morning with the windows up? I bet you keep your car set on fresh air when running the defroster, and then leave it in that setting with the heater, the smell is brought in through the vents because the car draws fresh air from the cowl.
Hope this clears things up for you, and it is something to discuss with the dealers to help more customers.