system too lean (bank 2)

i have a 2001 chevy silverado pickup it has a 4.8L and has apporx. 147.000 miles on it, i am getting a dtc. of p0174 and i looked it up and its a system too lean bank 2 i recently changed my fuel pump and filter i replaced the old pump with a gm part, my question would be, what is "bank 2" and what do i need to replace?