A highly porous ceramic filter consisting essentially of bonded ceramic fibers forms a part of an exhaust filtration system for a gasoline two-stroke engine. The porosity of the substrate permits accumulation of particulate constituents of the exhaust stream without detracting from the engine performance due to backpressure. Embodiments of the porous ceramic filter are disposed with a catalyst to facilitate reduction of gaseous and particulate byproducts of combustion from the two-stroke engine, so that emission of harmful pollutants is minimized.