According to GM, a “very small number” of 2013 Corvettes may exhibit an abnormal exhaust noise, due to an improperly torqued exhaust joint after the catalytic converter.

The torque spec may have been accidentally set at 11.8 ft.-lbs., when it should have been set at 19.9 ft.-lbs.

Replace the gasket if necessary and torque the fasteners to 19.9 ft.-lbs.