My S4 is not performing as expected. I only see 1800 - 1900 Gh/sec hourly ratings on Slush so far.
Have been checking the average for the last couple of days but can't see any improvement.
It is possible that your internet connection is throttling the throughput; for instance, if you are using wifi rather than an ethernet cable to connect to your router you may well see a lower figure; an ADSL connection down a phone line is likely to be slower than cable broadband; peak network usage may also slow things down at certain times of day. I have seen all of these play havoc with my own stats.