One problem related to other fuel system tank mounting has been reported for the 2006 Mercedes Benz CLS500. The most recently reported issues are listed below.
Strong smell of gasoline in interior of car along with smell in garage after overnight parking. Checked engine for leaks as well as general tank area. Negative. I think that the fuel sending unit (under rear seat may be loose or defective. Can't over emphasize the strong gas smell, while stationary--seems to dissipate on movement.