Probably the 'sound of power' is tricking your brain into thinking your gained uber hp. Seat of pants dynos are useless unless you really did something.

Do you have headers? If not, then no you didnt make a big gain. The thing with intakes and exhausts is, intakes dont do ANYTHING for power. And exhausts ONLY flow the amount of air that can pass through the THINEST part of the exhaust. So if you are still on stock manifolds...your still only flowing the same amount of air...just now it sounds prettier.

If you dont belive me...check a physics book.