This used to be done in the good old days before induction kits, usually on
XR2's

Allows more air in the air box thus, in theory, quickening response times, nb in more modern time espceially with turbos it would allow more hot air in which is not what you really want.
 
what it does do is give you more of an induction roar but at the same time allows hotter air in so reduces performance anyway