A stitched-panorama shot of the underhood area.
The Throttle Position Sensor (or "TPS") is an integral part of any electronically-controlled fuel system, even many carbureted systems. It is usually attached to one side of the butterfly valve which admits air into the intake manifold, while the throttle linkage is attached to the other. In carbureted systems, the throttle linkage may also have other functions; in fuel injected systems, it is the throttle position sensor which instructs the car as to how much fuel you are attempting to burn.
This is a Delphi Throttle Position Sensor that I purchased from autopartswarehouse.com.