This is a 'feature' of the DSM power steering system, which includes a speed-sensitivity feature that is intended to decrease operating effort at lower RPMs. This also means poorer response at high RPM, including the low speed/high RPM combinations required forautox.
DSS sells a modified power steering pump that fixes this problem - other vendors may as well.
Victor Del Col has worked out a fix for the high RPM cutout problem on 2G cars. There is a similar fix for 1G cars; a few details are available at this Calgary Area DSM FAQ page, and there is a VFAQ on how to modify the pump here, courtesy of Matt Price. [You would have found the latter VFAQ (hint, hint) had you checked the FAQ Locator.]