Fuel system

I knew that my fuel pump was going out and it finally failed the other day. I went and replaced the mechanical fuel pump and a year ago the fuel tank went to rust. I made my own tank in the back of the truck with two gas cans. I replaced the fuel pump but it seems as if the gas is not pumping fast enough to the carburetor. When I drive it in about second gear it starts to chug and almost stalls when I go to slow down like its running out of gas. I open the good and noticed air bubbles in the gas like it was bubbling at the entry point of the fuel filter. Any ideas as to what may be happening?