A hex nut formed from cutting and deforming a rigid planar material and having an integral attachment surface continuous with the deformable planar material allows attachment of the hex nut to any suitable surface. A dirt container is selectively mounted to the housing for receiving and retaining dirt and dust separated from the suction airstream. In some embodiments, an electric heater is utilized to perform this initial heating. A pressure difference between the pressure of fuel to be supplied to the at least one fuel injection valve and the pressure in the fuel tank is controlled such that the difference is at a constant value.