What are the functions of items?

The bandana gives you infinite ammo for all weapons except the Patriot Future Assault Weapon (it already has infinite ammo), and the Stealth camo makes you 100% invisible. Enemies can still hear Snake's footsteps, and the lasers that Gekkos and Scarabs target with can still see you. Collecting all 40 emblems will earn you the Snake Eater theme for the iPod. The Snake Eater theme increases LIFE restored by resting and other means, increases stun damage from all non-lethal weapons, keeps Snake's hands still while using a sniper rifle, and makes PMCs faint away when captured in a CQC chokehold. Occasionally while firing the Patriot, the Snake Eater theme will play.

Yes, the Bandana gives infinite ammo, the stealth gives invisiblity, but you need to crouch to prevent the enemy hearing your footsteps. The game completeion emblems gives you certian items, Eagle gives you the Desert Eagle(10inch), Big Boss gives you Big Boss FaceCamo, which makes your enemies afriad of you. Getting them all will reward you with MG3 Theme.

I have the stealth but not the bandana so ill tell you about the stealth camoflage!(*yayay yaaa yayyy*) So you use it in the items menu and equip it. It turns you transparent with a (blue) 100% camo rating. In a quiet place you should crouch because they will hear your footsteps. For good drebin points, Go up to a guy with a good gun and aim it at him(close quarters) and snake will say,"freeze"!, or,"drop it!" He will drop the gun and you will get extra points for this.(on liquid easy x 1.2 bonus) Than he has his hands up, knock him out by hitting him,or wait and he will take out a secondary weapon(not sure of malitia) repeat process.Hope I helped:P