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The air meter is Not part of the throttle body, it is upstream and is called the Mass airflow sensor.
The throttle plate is hooked up to the cable, AFTER the MAS.
and the THrottle position sensor is connected to the throttle plate.
Most injectors live after the throttle plate, but are mounted in the throttle body assembly. There are some exceptions on where the injectors live. Shower injectors hang directly above the throttle body, and spray into it, before the throttle plate.
Old type injection or the "batch type" was by way of a fuel distributor, and pump. Diesels still work on this principal today.
Bosch gasoline systems are like this, they do go into the head, but into the intake runners, and NOT the cylinder, they are more of a "mechanical type" injection system, and not an electronic one, like the systems are today. Randy...look inside that rubber housing, and you will see a disc, on an arm. it moves up and down, and controls how much fuel the engine sees. "Pre computerized as we know it....Injection System"
Where as sequential fuel injection systems, have single injector set on a fuel rail, that are activated by a voltage signal.
Port fuel injection systems are just that, the injectors are placed into the intake runners before the intake valves, and after the throttle plate. Direct injection into the cylinders, is usually meant for diesels.