From Mechanical Database
Actuators are the components of the Fuel Injection that make everything happen based on commands from the EEC with the help of sensors. Following is more in depth information about each actuator and how it works.
 Exhaust Gas Recirculation (EGR) This air valve allows engine vacuum to open the EGR valve. The EGR system recycles burnt exhaust gasses into the intake. This lowers the amount of fuel needed, and lowers toxic Nitrogen Oxides in the emissions. The EGR only operates at highway cruise conditions. |
 These are miniature electrical valves, which open and close to exact tolerances, metering fuel in exact amounts as commanded by the computer. They allow extreme accuracy in achieving calculated fuel ratios. They are mounted in the intake just before the intake valves, which improves fuel atomization. |
 A small device that adjusts the fuel pumps output pressure to a more consistent pressure for the injectors. |
 This electrical valve allows air to flow around the throttle body giving the computer control to stabilize the engine RPM. This advancement made no-touch starting possible. Keeps the engine spinning smoothly even with the A/C on and if emergency braking is required. |
 A small device that controls high electrical current devises. |
 Thick Film Ignition (TFI) This takes the commanded distributor timing from the computer and activates the coil. This advancement allows us to control and monitor timing without relying upon engine vacuum or weights. |
 Thermactor (Smog air pump) This pumps fresh air into the exhaust system, to burn left over hydrocarbons, lowering emissions. The computer uses 2 air valves (TAB & TAD) to control where the air flows depending on engine operation. |
Thermactor Air Bypass (TAB)
Shunts air to the atmosphere, when no air is needed. When air is needed it sends air to the second valve TAD. Thermactor Air Diverter (TAD) Diverts air either to the exhaust manifold, or directly to the catalytic converter. |
Article & images courtesy of fordfuelinjection.com.