Are you talking about the small holes located on each side the heat crossover portion of the intake?  If so, then the one on the passenger side has the choke chamber of the carburetor connecting to it with a pressed in tube.  This tube supplies the heated air to the choke coil on the carb.  The opening on the drivers side will typically have a small vent that presses in place to simply filter the air going across the heat crossover to the other side.