Originally posted by Impreza01
This was answered a while ago. The consenus was that in order for subaru to get all it's ulev ratings (subaru was recently given a ulev award by an environmental group), subaru programmed the cars to burn off the small amount of fuel still in the engine instead of having it dumped directly to the exhaust.
This is the theory that makes the most sense to me. VW/Audi 1.8 turbos exhibit the same characteristic, as does my buddies S4 (it's not the new one with a V8, it's the V6 bi-turbo).