smell gas

been having trouble with my 1989 cutlass supreme 3.1. It seemed like it was misfiring on me so i changed plugs and wires. I also had the igniton control module checked as well as all the coils on the car. They all came back testing good. After all this it still seems to maybe misfire and now when i turn it off i smell gas. Any suggestions on what could be the problem would be greatly appreciated. thank you.