[Dead Parrot]

Emissions to keep IMO:
PCV - keeps blowby crap out of your oil and the air
THERMAC - helps with warm up and preventing carb icing.
Vapor Canister - captures gas fumes from tank for later burning.

Much of the rest was an ad-hock pre computer pre injection pre catalyst kluge that often traded performance and/or efficiency to limit HC and NOx, with mixed results.

The reason so much is hooked to the thermostat housing is so it could either be turned on or off when the motor warmed up, depending on the gizmo in question.