Ok so you are going to be changing your S2, to EFI.

The flywheel.....only need it if you are going to drill your block and put the CPS there, otherwise no use. XR2i injectors are the same as FRST ones, you can use the XR2i loom with Turbo management, will need a couple of wires changes to run OFAB. Or you could put a whole XR3i EFI loom in , which will be the neater option.

The IAT sensor is different for turbo, and thats about it.