Turbo exhaust manifold, O2 down pipe, boost sensor, wastegate controller, radiator coolant feed and return, oil tapped feed and return, charge pipes, intercooler (including coolant pump, heat exchanger, coolant lines), ECM programming and probably a half dozen things I'm forgetting. Thus the reason it is much easier to purchase a turbo kit - unless you are good at scrounging and matching parts to work together.