I have the same problem. Its not because of a fuel leak, its because cobras have open vent gas tanks, unlike new passenger cars which have sealed airtight systems to keep gas from evaporating into the atmosphere. If you look closely at your car you will probably see a hose from the top of the tank running down, and its open on the end. The gas in your tank is slowly evaporating through that hose. At least thats what I found with mine.
Add to that all the crap they put into gas now days, MTBE, etc, here in North Texas we are getting the "winter formulation" right now, and gas just stinks.
Try putting some AvGas or racing fuel in it. At least it smells better.
