I am replacing the changeover valve in a w123 car (intake to distributor for idle increase while AC on). The original has 2 vacuum ports and 1 port to atmosphere. The replacement, Pierburg Part#: 001-540-86-97 has 3 ports (2 at the top that appear to be connected and 1 at the bottom. Are all 3 vacuum ports, or is one a vent to atmosphere? Input will be greatly appreciated.

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