Originally Posted by gsxr

The modulator should be adjusted so that WOT shifts are firm, with no flare or slippage during the WOT shift. You can adjust it either way as necessary to tweak the part-throttle shifts, as long as the WOT shifts remain firm & crisp. But there's no need to drive with the modulator disconnected (zero vacuum) since that will provide a full-harsh shift at all times.