Everything turbo related of course. The turbo, when these cars were new you could send in a core and get a rebuilt one, that’s what sort of wear item they were. The fuel pump, it is not set up like a normal tii pump so you need specialized knowledge to work on it, the manifold, no longer made and the turbo gets pretty hot and is poorly lubricated, the trans, either four or five speed has unique no longer made parts. Nothing is insurmountable, but if you have someone who works on lots of these like Brian (Preupy) and a few other mostly Cali based folks, then they have solutions to the problems that come up. Sometimes those solutions aren’t that quickly in coming I should add.
I’m not saying don’t get a turbo, in fact I think the opposite. But if you are going to use it a lot, as I do, you will be dealing with the inherent issues about owning a car that was designed and sold perhaps a bit before there was enough technology and knowledge to make it robust.