But you'd need to replace the doors with something can't just leave an open space.
Carbon boot is a massive saving, front strut bar changed for lighter after market. Believe it or not, but I saved 1kg just by changing my wheel nuts. Lighter clutch, lighter rotars, carbon doors l, wings etc. Just changing your oem brake hoses and brackets to braided hoses will save you another 1kg. Small amounts but they all add up. I've lost 66kg and probably more now that I've lost weight also!