External wastegate pipes

So I was figuring out some piping today and my external wastegate has four pipes.
Two are for water and iv got these plumbed in. Another one will be boost pressure but the other?
I can't think what it could be for. If anyone can shed any light on this it would be much apriciated.

What make is it ?

There we have a problem.
It has no name on it and before now, I had never seen one like it.
On my internet search adventures I have come across something which is nearly identical. The greddy externals are the same. Weather mine is a cheap copy or I can't find the greddy name on it I'll never know. I'll try and get a picture up.

So the bottom pipe is water. As is the one with the blue pipe on behind my catch tank.
The one with the black pipe on and the one with nothing on are the unknowns.