envy your gmat score. i wish for exchaning it with my toefl.
for gmat cracker, it's no wonder to get 29+ both in reading and writing. yr writing is terrible. 21 is not acceptable by any graduate program. work harder on it, don't look it down.
if you keep listening to toefl questions in the past, mainly long lectures, after a month or so, you should be able to score 25+ in listening since you have no troubles with vocabulary.
speaking: it's a matter of speaking habit. if you speak Chinese clearly and coherently under timed circumstances, you'll hopefully work out after two weeks practice. 22+ is actually not so hard.