bars are good, if they're dirty thirtys they're already a very light bar.
stem can go.
do you know if you forks have a steel spring? see if you can find a titanium one if not, i have one lying around.
front rims heavy, get a mavic 721 instead and that would save a couple hundred grams
roadie seat and carbon post of ebay.
that should have a maybe half a kilo?
light xc tubes, or ghetto tubeless.