It is called the rack position sensor and one of the inputs for the egr control unit. You can have that there with no effect on drivability. I have that on my car but the EGR disappeared for a while
I dont know any thing about an electric servo in the turbo of an '85. He must be talking about the air recirculating valve which is controlled by a switchover valve and controlled by the EGR control unit. Some have theirs disabled with no problems reported. I think you can transplant the '85 engine with no problems as long as it fits the engine mounts. I wouldnt replace the turbo or the injection pump. I would go for the original from the '85. Most of the problems mentioned are emission related.