Ford Repair: Ford Escort - Heating Vent Problem, petrol fumes, 1997 ford escort

Question
I have a 1997 Ford Escort.  Past few months there has been the smell of petrol fumes through the air vents when I turn on the heating.  There is no smell on cool air.  Two garages, including a ford dealer have said the engine is dry with no leaks - but I don't feel any easier about it.

Answer
a very, very small leak can give off an odor when it is gas that evaporating-with the engine warm and running open the hood and look around your fuel lines and injectors especially the injectors-look on the side and see if any of them are even slightly moist or shiny if so the housing may be seeping.