Induction kits eliminate the standard airbox, which can be restrictive. An open high-flow cone filter is used in its place, the filter used is supposed to be less restrictive and allows quicker air flow into the engine (more air=more fuel= bigger bang).
Be warned though, because the cone filter is exposed-it is more likely to draw in warm/hot air from the engine, which will actually hinder performance........the standard airbox actually sheilds the standard filter from the hot air and brings in colder air from the front of the engine.
So, if you are going to use an induction kit, it is advisable to purchase one with a heat sheild.
and also, most cone filters, if not all, are sprayed with a protective oil, this oil can foul up the MAF sensor and cause issues.