Tank Mounting problems of the 2004 Mercedes Benz E320

While driving I started smelling gas, especially when I would have just filled the tank. This smell went on for years, it got odor got stronger and stronger so finally I went and got it diagnosed and my mechanic said that I need replace my fuel pump and showed me the gasoline under the rear seat (rear driver's side) the amount of gas was so great that I called and asked my rep at mercedes if there was indeed a recall on the part and I also told him that my mechanic said that there should have been a recall on it , and still he said no. So I replaced the part on my own. Now I am smelling the fumes again, I take it that it is coming from the other side. I have to ride with my windows down and/or sunroof open to keep from getting the head-aches again. This have been ongoing for years now . I purchased the car in Jan. 2008.