i think your fuel rail or something associated is leaking, and the vapors are getting to the HVAC fresh air inlet located at the base of the windshield.

to try and find the leak:
1. park your car in a very well ventilated area, preferably with a fan blowing into the engine bay.
2. start the car, you dont have to let it warm up. in fact it may be safer to do this with the engine cold.
3. pull the vacuum hose off of the fuel pressure regulator. this will cause the fuel pressure to rise to max.
4. follow all the fuel lines in the engine bay to make sure you dont see any fuel leaking out of them. then look around the fuel rail and injectors to see if you are leaking there.

thats about it to check for a fuel leak. and remember NO SMOKING!!!