Sorry for the confusion I caused on the environmental var ... you are all correct ... it is SWAN_SYNC.
The only time I see WU that slow is after a driver crash and the GPU goes into a low power mode ... I have precision 1.9.2 and it will show what speed it is actually running, not just what it is set to. Once the driver resets itself the only way to back up to full speed is to reboot :-(