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Have you allowed for tubeless sealant in your 550g for tyres? That'll add 50-75g if you haven't.
Easy 50g to be saved with a UNO stem... knockoffs can be had for cheap too.
Getting 2/cages down to 20 odd grams is easy as said above with the XXX light knockoffs.
130g Hylix seatpost (use at your own risk).
Plenty of non-boutique saddles at around 100g - stripped carbon SLR for example will be 110 or 115g (they fit me, but YMMV).Could easily knock a big chunk more off on wheels, but $$$
this isn't even extreme weight weenieing and it would still be p.expensive