u really need all three to get the best gains...cuz what's the point of having freer air flow out the exhaust...if it gets all restricted coming in...exhaust has basically negligible gains...cai has some decent gains up top...header has some decent gains too...but short ram or resonator and drop in don't really do anything...short ram especially cuz it's just sucking in all this hot air...which doesn't hav emuch oxygen...so get intake header and exhaust