AFAIK, the 4163B with A104 firmware can only overspeed certain 8x DVD+R disks 12x. It won't overspeed any other speed of media and it won't overspeed -R media either. Not sure about RW disks though.
You can try using MediaCodeSpeedEdit though. You might be able to overspeed 8x disks to 16x with that but I do not know for sure. More info about that in this thread.