Heat recovery steam generators are an essential element in combined cycles. They take the waste heat from the gas turbine exhaust gases and produce steam that- upon expansion in a steam turbine- delivers additional power. Supplemental duct fire burners increase the heat of the gases as well as the steam production; the exhaust gas flow ignites and keeps burning high by using the residual oxygen in the gases to feed and form the flames, therefore its distribution needs to be homogeneous to prevent the flames from quenching and lowering the heat transfer. In recent research several designs have been analyzed- using computational fluid dynamics- looking to improve flow conditions by adjusting geometries or adding flow correction devices. This paper addresses the exhaust gas flow distribution from a combined cycle cogeneration plant from a previous study that integrates a diverter valve in the transition gas turbine-heat recovery steam generator and proposes a methodology to improve non-uniform flow patterns. The paper focuses in the attack angle of the duct burner baffles and the use of flow correction devices already installed in the system. The analysis has its core on structured experimentation carried out by means of computational fluid dynamics, being able to predict flow behavior with statistical bases.