Racer X owner...
Howdy, I also ride a Racer-X, one of not too many in Australia- but thats beside the point. Having my RX down to 23.8lbs and hopefully down to 23lbs by the end of the Aussie summer makes me botice a ffew things that you could save weight on. Not all are really practical, most reasonably cheap, but toehrs more expencive...
Anyways things that stand out as easy pickings are.
Crank w/ BB Dues 175mm: Check out this thread
Click HERE! , just quiet recently was up on the board- looks for my thread, has abit of info on weight savings. you can quiet easily save 40g+ on these cranks, or even get them to 785g if you want... (Stock weight 830g+).
Fork F100X: Do you like the lockout / terralogic? If not the weight can be taken out of these forks, by taking out the terralogic... OR buying new forks, Private message or email me if your up for selling them

You'll save about 100g+ if what I read on WW's is correct. Personally I prefer a fully active fork.
Shifters X9: An X.0 Grip Shift and X.0 rear derailleur is a great combo adn will save a fair bit of weight- nothing great, but it also improves the shifting preformance in my opinion - I run full X.0 on my bike and it is sweet - grip shifters are for every one though. Save maybe 80g?
R derailler X9: As above...
Headset Chris King: You'd be stupid to change this
Cassette SRAM 990: If you are running the 11/32 it weights around 270g - swapping to XTR will save you about 30g Dura-Ace will save 90g, but isn't practical for every day use in my opinion; for racing yes. I quiet like my SRAM PG990, comming off a Dura-Ace 12/27 I find that although I am a fan of close gears- the 11/32 pedals better on the Racer X. Save 30g to 90g?
Stem Richey WCS: Syntace F99, weighs 100g and is said to be as strong as the rest. Save 25g to 40g
Seatpost Thompson 287mm: Much lighter options about- whether you trust them or not is upto you. weight can be saved machine the seat clamp, I saved about 20g by machining some material off.
Pedals Candy Ti: Twin Ti EggBeaters will save you some weight if you can handle no platforms. I love my Twin Ti Eggies. you save maybe 80g?
Tires WTB weirwolf 2.1: Loads of much lighter, and much better tyres out there- I'd change these for some Kenda DTC's, Schwalbe, Conti,s or verious others all have better roling resistance and are alot lighter. Save maybe 50g to 100g+ per wheel
Tubes generic: Eclipse Tubeless- not so much saves weight although it does provide more grip, and flat resistance due to lower tyre presures. Will save you abit of weight also.
Grip Oury Lockon: Foam - foam grips are the way to go in my opinion- they weigh about 20g, and are comfortable; I hang on to mine for upto 12hrs at a time... I should know.

Saves 40g to 80g
I hope that helps- as I said not everything is practical, and somethings are a compromise you might not want to make- which is fair enough. I love the way my bike is at the moment- All I have got to change is the wheelset, stem, chainrings and forks and I will be sitting on about 23.1lbs for a well rideable Endurance Race / trail bike.