It's worth pointing out (for the benefit of the OP) that an induction kit will not actually increase the total amount of air that can go into the engine, only forced induction (and perhaps ram scoops) can do that.
What it may do though is reduce the restriction on air flowing into the engine, meaning that an engine will breath better across a wider rev range than the stock filter.
This helps engine pick up faster (as it's not struggling to suck air through a restrictive filter) and thus may restore some hp lost where the engine was being held back by the resistance of a restrictive air flow.
Where it may provide "more air" is during higher revs, where air flow may have been so restricted that cylinder could not fill fully during the open inlet valve timing.
However, if such a situation existed, then a restrictive exhaust would have to cope with situations, especially at higher revs, when there is now more exhaust gas to dispose of (as the cylinders will be filling fully, where they were not before). This may cause an increase in backpressure as the engine tries to ram all this gas down an inadequate pipe and subsequently an increase in both heat and burnt gasses remaining in the cylinder. This would mean that the cylinders would now not fill properly again as they will be half full of exhaust gasses.
So, as has been pointed out, an induction kit probably won't make much difference to power unless coupled with a freer flowing exhaust system, and then it will only push the engine a small way to achieving it's full displacement potential.
