Abstract: In a diesel engine equipped with a catalytic HC reformer for injecting reformate into the engine exhaust stream to reductively regenerate one or more emissions control devices including but not limited to a lean nitrogen trap, a combustor is disposed in the exhaust stream downstream of the LNT, and preferably downstream of all regenerable emissions control devices, to burn any residual HC, H2, or CO in the tailpipe exhaust gases. Thus only breakthrough amounts of these species are combusted. Preferably, the combustor is operated on an appropriate schedule governed by the operating schedule of the reformer. To assure combustion when the oxygen concentration of the exhaust falls below the reformate combustion limit of approximately 6%, make-up air is ported to the combustor either by diverting a portion of the reformer system air or by diverting excess turbocharger boost air from the engine air intake system.