you will notice more sound coming from your engine bay while your in the truck, how much will may be determined by what system you buy. like a k&n system with a metal pipe is gonna be loud the plastic pipe version has a deeper sound to it, and if you decide to go with a trd or afe you'll notice the engine has more of a growl to it and if you want it louder youyou can remove the lid which may or may not effect power. my vote is for trd or afe ive heard a few of the k&n systems and it you seems to get the sound of the injectors ticking gives it a real crappy sound at idle.