Chiaotzu was probably more a buddy who hanged out with Tien than a training partner by that time. Even then his potential is still most likely much lower than Yamcha since he didn't show up for the Androids or Cell games even through Yamcha did.
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http://img401.imageshack.us/img401/33/shadowkenj.gif
LOL!!!! I hope that's a joke....names don't get more n00bish than that