If you are referring to an actual 'stinky' smell, you could be experiencing anything from burning oil or coolant, to worn brakes or clutch, or even mildew in the Air conditioning system.
If you mean your car 'stinks' in a more figurative way, then I'm not sure i can quantify a reasonable explanation as to why the Aston martin experience has been at all below your expectations.
Either way, at 12,000 miles, i would suggest returning to the dealer from which you purchased the car and have them address the issue at hand.
There could be something wrong in the computer controls causing a backfire (like a problem with the electronic timing control). Take it to the dealer immediately to avoid possible engine damage. Is the vehicle still under warranty?