If it’s not been messed with too much there’s a plastic cap on top of it and it’s on the carburetor at the top right near where it mounts to the manifold
Typically an “Air Idle Control Valve” is part of a fuel injection system Carbureted engines typically have a needle and seat adjustment, and depending on how the carb is designed can control either the amount of air or fuel entering the idle circuit. Please go to the top of the page, click the link, and fill out the information on your truck, in the signature of your profile.
