Looks like its on the Cold Air Intake tube, so that would be for the air pre-heater tube/hose from a shield around exhaust manifold on that side
All vehicles had these since the 1950's
The tube is flexible and looks like a drier air vent tube but for higher temp, like these:
https://img.directindustry.com/images_di/projects/images-g/air-intake-pre-heater-hose-147109-18102953.jpg
On cold start the thermal switch(not electric) would open a vacuum port and move the valve inside the part you took a picture of
This would then pull in air from around the now warming up exhaust manifold, pre-heated air
This would help the engine warm up faster
Thermal switch would then close and Cold Air Intake port would be open
This system was not required for proper operation of the engine system, so often left off after engine work
It does help engine to warm up faster which WILL lower emissions on cold starts
So in Calif and some other areas they do check that its there and hooked up, if not you would fail
This is what a shield can look like:
https://i.ebayimg.com/images/g/eo8AAOSwL-1jEP-I/s-l1600.jpg
Bolted to outside of exhaust manifold, you can see the large black vent hose on the right, its a V8 engine so larger hose
Just sucks in pre-heated air for faster warm up