On mine the rear port connects to wiper hose. The front port connects to manifold. My AC dual pump looks a bit different that the above posted one.(ports). I put a brass elbow on the manifold.
On a side note under the dash I put a "Y" fitting where the wiper hose comes in. I added a valve and it now runs my small original Trico fan. Just turn the valve back and wipers work. I love the vacuum set up. Todd
