As above, I have stripped a few basic things out from my 197 to save almost 20kg including rear quarter foam, under bonnet foam pad, unnecessary items from the tool kit, rear wiper assembly, modified acoustic valve, headlight washers, heat guards from rear diffuser and above rear backbox and ISOfix bar. Also, 200 Cup wheels are about 1kg lighter per wheel than all over 197/200 wheels. I have plans to save another 20kg from modifying the front seat subframes, battery, replacing the standard exhaust (weighty) with a resonated Milltek and decat.
Rear seats is an easy way to save another 15-18kg for regular 60/40 split seats although removing the rear seatbelts requires resistors to not bring up an error message. Cup suspension is marginally shorter than full fat so a tad lighter. Proper Cup doorcards save a little bit. Lighter battery can save as much as 10kg and be a fit and forget item.
For me, I dont want to sacrifice useability, driveability or comfort as its a daily. I am toying with ditching air con to save another 15kg or so but I enjoy the stereo and have added some rear speakers, and equally love the factory Recaros (the subframe is the heavy and overengineered bit) If it was a weekend toy, Id ditch the rear seats, boot carpet, plastics, air con, lighter wheels, a non resonated exhaust system, etc.