Boost bottle

Supposed to act similar to a capacitor in an electrical circuit, accepting some air/fuel charge when the induction cycle closes off.

The charge is then said to be added to the next induction cycle adding extra boost to that charge.

Some say it aids in smoothing out the pulses in a multi cylinder equalisation tube.

Pro: They add some bling.

Con: Just another thing that can give you trouble.
 
pro's... find the right size cork and they hold almost a pint of rum !