The GM designed system has a Pressure Module which is continuously monitoring the pressure in the fuel line and sends enough Voltage to the pump to keep the pressure where it needs to be........Because I didn't use the6L90E transmission......we couldn't use the ZL1 system.........So.....Carl at Vaporworx developed a stand alone system that has a pressure monitor that is installed into the fuel line just outside the tank........the module supplied basically reads the fuel pressure just as the GM system and varies the Voltage to the ZL1 pump just as the stock GM designed system.......So.....There is not a return line..........the Pump only runs as hard as the demand put upon the engine
http://vaporworx.com/