nothing... it just traps some of the incoming air flow to essentially make the engine quieter
i usually have the whole plastic part of the intake removed, its jsut on there because i need to smog it soon. i actually regularly run my intake with jsut the air filter base (air horn as they call it on chevies) and this setup:
I'd do that, but I'm looking for a true CAI. It'll probably be redesigned for smoother flow also. Are throttle body spacers any good on these things?