An apparatus for mixing a first fluid into a flow path of a second fluid, the apparatus comprising: a chamber enclosing the flow path, the chamber including a second fluid first inlet for receiving its respective fluid. The apparatus also includes a second inlet arranged downstream of the first inlet and receiving the first fluid, as well as an outlet arranged downstream of the second inlet for discharging a mixture of the first fluid and the second fluid. The second inlet flows into the flow path and is formed by a shared fluid injector mounted transverse to the axial direction that one fluid and the two fluid flows through its chamber. The flow path includes two respective throttle bodies, each of which is pivotally arranged inside the chamber and attached to opposed sides of the chamber for controlling the flow area of the flow path.