Here's the service schedule for an IS200 - http://i2.photobucket.com/albums/y45/DataB...0MaintSched.jpg
An Altezza will be similar minus the cam belt. That should be done at 100K rather than 150K.
Assuming your car hasn't had the 75/80K done in Japan then I'd changing your fuel filter. 90K would have been to replace the spark plugs, air filter, brake, diff & transmission fluids. It's more than likely it wasn't done either.
If you're going to change fluids then I recommend using fully synthetic & make sure use the correct GL rating. GL4 in the 6MT & GL5 in the diff.