The GS300 has a saddle tank with a hump in it where the drive shaft passes through. It sound like the fuel from the passenger side of the take is not being transfered over to the side that has the fuel pump in it. A simple test would be the next time you run out of fuel remove the back seat and then the fuel sending unit from under the passenger side rear seat. If you see a lot of fuel then it is not transferring. There is a tube that comes from the passenger side to the fuel pump assembly on the drivers side. A device on the fuel pump assembly creates suction to bring the fuel across. If this device is broken or the line is kinked it will not work.
Ben
