Actually, I looked up the diagram for a gas fuel injection system (Google) and all images showed a low pressure (transfer) pump in the fuel tank and a high pressure pump outside of the tank.
I was a marine mechanic and when we replaced carbureted engines (gas) with fuel injected engines we did not have to install any pumps in the fuel tanks. The engines are GM products (Crusader or Mercruiser). We just connected the existing fuel line to the engines.
Freepmail me the links.
I work on this stuff all the time and am confused by your description.
Here is a typical one
http://www.icarumba.com/includes/content/resourcecenter/encyclopedia/ch15/15Fig22.html