If your script is running at a solid 60 FPS, then vsync is most likely on. Can you make sure power management is not enabled in the nVidia 3D settings. The setting should be called "Power management mode" and you will want to make sure it is set to "Maximum performance".
Also, this is not ideal, but try enabling the 'viz.glFinish' option:
Code:
viz.setOption('viz.glFinish',1)
Let me know if any of these make a difference.