EVERYTHING ABOUT B16 ENGINE

Can n e one particular explain to me which kind of gain in hp i must b receiving? Also so i'v looked at getting a mugen air filter an box to but there v expensive, dose n e one no if its value receiving 1 an what attain I would get from it. Thanx AshtonA single large reason the B16 engine is so renowned amongst JDM fanatics is horsepower per liter.