The 2003-2006 E55 (with the issue framed as spanning the 2003-2009 E series) is known for gasoline leaks and fumes from the fuel pump/sender/tank top assembly, subject to a class-action and a Mercedes warranty extension on the pump assembly to 15 years/unlimited miles. Buyers are advised to check for a fuel odor and whether the pump/sender has been addressed.
Early E55 fuel-tank / fuel-pump leak defect and extended warranty
Mercedes-Benz E55/E63 AMG (W211) · mechanical