That's the A/C idle up systemà dunno if your truck still has it, but originally there was another diaphragm on the throttle lever that idled the motor up when the A/C kicks on. That's where the hose goes.


My Truck: 1987 XtraCab DLX 22R 4WD 5 Speed Manual
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"Speed has never killed anyone. Suddenly becoming stationary, that's what gets you." -Jeremy Clarkson