Can anyone help me identify this exhaust component?
 

Hello I have a 1986 NA 300zx 2 seater. Last summer I noticed that the engine started sounding like a weed whacker so I jacked the front end up and began looking for an exhaust leak. Underneath the engine I noticed coming down off of the exhaust manifold down pipe (after the two pipes combine) there is a metal tube that connects to another metal tube via a rubber tube which was dry rotted out. I replaced it with a piece of radiator tubing which quickly burned through and fell off again. So for the mean time I made up a fitting out of radiator tubing and a piece of copper pipe. It's lasted for 4 months now but I wanted to know if anyone could actually identify what the part is called so that I can order a true replacement if the current repair fails. I can't find the name of the part even in the factory repair manual I have. The tube runs up along the drivers side of the engine and it hooks up to something that appears to be a part of the emissions system. I have some pictures of the fitting I made up and where exactly the line runs, any help would be appreciated I've checked out zbums microfiche to find a part and I can't identify it. Thanks in advance!

EGR tube.

Also moved to Z31 section.

EDIT. Lastly, download the FSM for free: www.xenonz31.com/reference.html

Thanks I have the FSM, I don't believe it is the EGR tube though the EGR is located at the back of the passengers side of the engine while this is located at the front drivers side next to the AC compressor

I found it, air injection valve, just not sure where to find the tube but for anyone else with the same problem it is called an A.I.V.