I noticed in the little hatch the Turbocharger is selectable in the slot in the parts list, though in the jbeam files the "turbo" is just coded as a separate engine. Is this just a placeholder and are turbochargers going to be implemented correctly in the future?
Yes, right now there is no way to properly "modify" existing things (like the weight of a node, or a torque curve) so the turbo just overwrites the torque curve of the engine.