I assume original system is closed to the atmosphere. Why not make a 2 or 3 foot detour pipe (between valve cover and intake) of same diameter and use filter material found in kitchen exhaust fans. This length of pipe will allow fumes to cool and condense in the filter material. The oil fumes would settle in pipe and filter and they would only need to be cleaned. Perhaps even two pipes of smaller diameter could be used because of the greater cooling area.Just wondering....hmmm!