So I need to change this hose that I circled in red but I don't know what it is or how big the diameter is to order a new one. Apparently its plastic and not rubber how I thought. And I thought it was maybe a vacuum hose but I was told its not, that is something with the turbo. Correct me if i'm wrong, it connects to the manifold from another hose that comes off from the intake. Any help recognizing what this hose is greatly appreciated!

Its a 1989 740 turbo

 

Just go to a real parts store, one that sells hoses by the length, and bring the old hose with you, they should be able to help you, it's not a big deal, nothing special about it. I don't recall the diameter off hand...