disa manifold wiring question

So I have the disa manifold and spoke with the BMW mechanic who will do the install next week. He had a question that had also occurred to me, that is how does it hook up to the engine wiring? I was hoping that the hook up would be already in place, but wondered why it would be on a stock 128 engine that had no disa components. Can I assume that the wiring is there and will be obvious to the mechanic once he gets in there? I know several of the forum members have done this so it may be a dumb question but I want to make sure I have everything needed.