Abstract: The method of treating a fuel lean exhaust containing NOX and SO2 includes splitting the exhaust into major and minor portions for flow through multiple flow paths each of which contains a particulate trap and an absorber containing a NOX oxidation catalyst and a nitrate absorbent. The major portion is passed through a flow path in the lean state at a first temperature to convert the NOX to nitrate and the SO2 to sulfate. After the first period of operation flows are switched so that one flow path receives a minor exhaust portion for a second period of time during which fuel is injected into that flow path along with diversion of a portion of exhaust from another flow path through a bypass.