BBS = big brass screw on each throttle body.
before you do anything turn them in to lightly seat them,
noting how many turns,
then return them to original position,
the close to run setting SB about 1 1/2 turns out.
You may also want to remove the throttle bodies from the intake rubber mounts,
and inspect the sealing surfaces if one of the seals is leaking then the engine wont run properly