What the two lines to the carb do:

One feeds the carbs float bowl... You have to hook that one up!

The other is a bypass line that does not supply any fuel to the carb! What does it do? Since some small amount of fuel is always going back to the tank it keeps the fuel from getting too hot from sitting in the lines. On its way back to the tank it runs by the accelerator pump to hlpe keep that part of the carb cool.

The accelerator pump is still fed from the carb bowl and the primary fuel line connection.

If you connect up the this second line it needs to have some sort of restrictor of all your fuel pumps capacity will be used to pump fuel in a circle back to the tank. Look at the restrictor in the stock fuel pump for an example.

If you dont do this you will have your pulse type pump working harder than it needs to and that will shorten its life.

Kevin C