Belt Cad Need Help DX. A Problem W/a 1992 Cad. Sev. STS?

Need help DX. a problem w/a 1992 Cad. Sev. STS? - belt cad

After about 15 km. Reductions in the car and the smell of gasoline vapors. Replacing the fuel filter as the belt tension and replace Pulles idly, without success (which replaced anyway). OK rpm. Dx Can anyone help. they receive or a suggestion about the problem? 2 friends to this situation are confused. If a rotor or spark plugs? Thx in advance ... dying to hear you. Patti