I purchased a 2011 Chevrolet Impala last year with 14,000. When the car reach 26,000 I begin to smell a very strong sulfur smell coming from the exhaust. I took the car to the local Chevrolet dealer and was told that the particles in the catalytic converter begin to break up at about 26,000 mile and the result
is a sulfur smell. I didn't believe that all Impalas had this problem. So I took it to the Chevrolet dealer in the next town where I personally know and trust the maintenance chief. He put his two best men on the car and could not find anything wrong. I was told to try another gas station which I did but it did not help. I now have 31,000 miles on the car and the smell is very strong coming into the passenger compartment when stopped. Can you help?