Where is the air sensor on a 97 Geo Metro?

The IAT Sensor (Intake Air Temperature Sensor) is located inside of the air-cleaner assembly. You will see it near back (towards the cab of the car) when you lift up the air filter. It is plastic and looks like this: http://i442.Photobucket.com/albums/qq146/coolaj86/017.jpg. You'll only see the rod-looking part from inside.

If you are talking about the air charge sensor it mounts on the firewall passenger side and has a vac hose that runs to the base of the throttle body and a connector into the elec harness