I need the part number for the plastic elbow that attaches to the heater core to penetrate the firewall. Please post a part number or name. Any site that has this or number i can call would be appreciated as well.

 

You didn't give a whole lot of information, but I think you're talking about this part 9223140U00 ? It's for a 98 SE with manual a/c. This is a great site for Nissan part #s. Check out #20. Could be what you're looking for.