1. Top Vacuum Port: This port is used for the EGR modulator, which controls the vacuum signal to the EGR valve. The line from this port runs to the EGR modulator, which is located on the driver's side inner fender.
2. Middle Vacuum Port: This port is connected to the vacuum reservoir. The vacuum reservoir is located near the battery on the driver's side of the engine bay.
3. Bottom Vacuum Port: This port is used for a timed port injection (TPI) system, if equipped. It will typically have a small tube that connects to a vacuum source near the throttle body.
