It's usually not a good idea to leave a broken vacuum hose unrepaired. There will be unmetered air entering the intake manifold resulting in a lean condition. If you want to disable the VIS you can plug the broken hose at the source side to eliminate intake of unmetered air. The PCM activates the VIS vacuum motor at 3,000 rpm to shorten the intake runners length. If you normally drive at low engine speeds then you would want to keep the runners at the longer length to improve torque. If there is no vacuum to the vacuum motor then nothing will change at 3,000 rpm.