Sorry to bring this up from the dead, haven't been on for some time. That filter that goes between the engine and brake booster IS for gasoline fumes when the engine is not running. We installed them on cars in 1977 as part of a recall at the Olds garage I was working on at the time. Apperantly a couple of boosters failed and caused accidents. If you don't have one I wouldn't worry though, boosters went without the filters for years. Jay
