A system for treating diesel exhaust is disclosed. The system includes a first filter including layers of filtration material positioned between layers of corrugated metallic foil. The metallic foil defines a honeycomb arrangement of longitudinal passageways from an upstream end to a downstream end and also openings for allowing exhaust to pass between adjacent longitudinal passageways of the metallic foil. The filtration material is positioned such that exhaust between the adjacent longitudinal passageways passes through the filtration material. The metallic foil also includes flow diverting structures to divert flow within the longitudinal passageways through the openings. A second filter is positioned downstream from the first filter. The second filter defines a honeycomb arrangement of longitudinal passageways. The longitudinal passages are selectively plugged adjacent upstream and downstream ends to force flow radially through walls between the longitudinal passages of the second filter.