The present invention relates improving the performance of nitrogen oxide reduction by exposing rich exhaust to catalysts systems comprising a catalyst, wherein the catalyst systems are free of platinum group metals. The present invention also relates to improving reduction of carbon monoxide and hydrocarbon in exhaust by introducing air into a portion of the exhaust between a first catalyst system and a second catalyst system. The present invention also relates to improving nitrogen oxide, carbon monoxide and hydrocarbon reduction by (1) exposing rich exhaust to a first catalysts system, wherein the exhaust has an R value of greater than 1.0 and the first catalyst system comprises a catalyst and is free of platinum group metals and (2) introducing air into a portion of the exhaust in between the first catalyst system and a second catalyst system, wherein the second catalyst system is free of platinum group metals.