I saw, on a power stroke, a cloth type pre-filter covering the air filter cartrige. This pre-filter looked like a piece of silk. The very fine dirt was laying on this silk type cloth and was easily brushed off. There wasn't any oil medium. Does anyone know what I was looking at? Does anyone know what a guy can get one for a Dodge. Forgive me for looking at a Ford, the owner was showing me the prefilter but he didn't know where it came from.