A module for controlling a first fuel rail pressure in an internal combustion engine and maintaining a predetermined pressure bias with a second fuel rail pressure, both first and second fuels being directly injected into a combustion chamber, said module comprising: a manifold body comprising an inlet into said manifold body for receiving said first fuel into internal fuel passages defined by said manifold body, and an outlet from said manifold body for delivering said first fuel to a first fuel rail; a pressure regulator for controlling the rail pressure of said first fuel as a function of said second fuel rail pressure which is used as a reference pressure for maintaining said pressure bias, said pressure regulator comprising: a first inlet for receiving said first fuel which is fluidly connected through a first passage provided in said manifold body to said inlet of said manifold body; a second inlet for receiving said second fuel; and an outlet for delivering said first fuel with said predetermined pressure bias, said outlet being fluidly connected through a second passage provided in said manifold body to said outlet of said manifold body; a check valve having an inlet fluidly connected through said first passage to said inlet of said manifold body and to said pressure regulator; and a shut-off valve for shutting down fluid flow to said first fuel rail, having an inlet fluidly connected through said first passage to said inlet of said manifold body; wherein said pressure regulator, said check valve and said shut-off valve are components installed on said manifold body to form a unitary and independent structure which allows fluid communication between said components through internal passages in said manifold body while allowing flexibility of moving said components together as one structural unit. a manifold body comprising an inlet into said manifold body for receiving said first fuel into internal fuel passages defined by said manifold body, and an outlet from said manifold body for delivering said first fuel to a first fuel rail; a pressure regulator for controlling the rail pressure of said first fuel as a function of said second fuel rail pressure which is used as a reference pressure for maintaining said pressure bias, said pressure regulator comprising: a first inlet for receiving said first fuel which is fluidly connected through a first passage provided in said manifold body to said inlet of said manifold body; a second inlet for receiving said second fuel; and an outlet for delivering said first fuel with said predetermined pressure bias, said outlet being fluidly connected through a second passage provided in said manifold body to said outlet of said manifold body; a first inlet for receiving said first fuel which is fluidly connected through a first passage provided in said manifold body to said inlet of said manifold body; a second inlet for receiving said second fuel; and an outlet for delivering said first fuel with said predetermined pressure bias, said outlet being fluidly connected through a second passage provided in said manifold body to said outlet of said manifold body; a check valve having an inlet fluidly connected through said first passage to said inlet of said manifold body and to said pressure regulator; and a shut-off valve for shutting down fluid flow to said first fuel rail, having an inlet fluidly connected through said first passage to said inlet of said manifold body;