problem solved, just in case anyone else is wondering. the 3f has 2 charcoal canisters (on the 88 model fj75 anyway) one is to do what a charcoal filter would normally do and that is capture the fumes from the fuel tank until the time your engine is running and that filter is on the drivers side near the fuel filter. the other charcoal canister i was referring to (on the passenger side next to battery) serves the same purpose as the other one but is for the vapours released from the carby's fuel bowl not the tank. with the fuel vapours in the fuel bowl so minimal it's as good as gone, no other carby ive seen has this so i can't see why it is needed.