Some will say 12HP at the wheels, but please don't believe the hype. Real world results and inflated manufacturer HP claims are two very different things. It's not going to give you much power, but it will improve throttle response noticeably. I'm guesstimating maybe 5-7HP, but the sound you'll get from your motor is priceless. It also dresses up your engine bay pretty well. Since money is of a concern, just go with the Fujita since they both achieve basically the same results.
Check here :
zerothread/304846 because the guys on here are trying to get a group buy from Stillen on the Injen's. If the price difference between the two intakes are only like $40 or so, I'd definitely go with the Injen.