Cooling system rb20det

[A31cefiroNZ]

Hey all so anyways having trouble with the cooling system in it, now have a hose running under intake and beside thermostat have plugged in the long hose running from firewall side, also plumbed the smaller port which was under it, as old engine was like that, now back toward the firewall have plugged I the shorter hose from firewall side, but am left with another plug that is a coolant/water hose, just wanting to get an idea of what it could be and where to plug it? It's the port closest to the firewall, one over from it is where have plugged in the coolant hose, any idea of where it could plug it as I don't have an extra hose there to connect it but I left a hose there on the new block and water/ coolant is coming out of it.....