You should see a dr, preferably an ENT. Smelling gas/exhaust fumes is a common symptom of phantosmia which has many causes. I haven't heard of anyone having the sweet taste as well. An ENT might be able to give you a diagnosis as to what is causing your smell and taste problems. Many drs are not aware of these issues so you might want to research parosmia (distrotion of smells), phantosmia (smelling things that aren't there phantom smells) and dysguesia (sp? - disorders with the sense of taste). I would recommend that you print out any information from reliable sites that you find to take to the dr.
I hope you find some real answers soon and find a good dr who will help you.
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