A burner module for burning injected reformate mixed with engine exhaust in an exhaust pipe ahead of aftertreatment devices, comprising an exhaust flow divider that creates a localized region of exhaust flow for mixture of the reformate. The amount of reformate required to produce a burnable composition in the localized area is less than what is required in the prior art to provide the same composition over the entire cross-sectional region of the exhaust pipe. An igniter is provided within the localized region. Upon ignition of the reformate, the flow of reformate may be increased to the point of a stoichiometric mixture for the entire exhaust, to produce the maximum heat for warm up. The exhaust flow divider may comprise a divider tube mounted in the exhaust pipe or may be simply a protrusion from a wall of the exhaust pipe.