vacuum line/throttle body

I have a 96 Buick Regal with a GM 3800 series 2 engine. The previous owner had a few less than honest mechanics work on it and they kinda rigged the vacuum lines a bit. The throttle body has what looks like 2 vacuum line connectors but the vacuum diagram only shows the lines connecting to one of the ports with no explanation for the other one. Could you please tell me what the other port is for and what needs to be connected to it (if anything at all).