There is no Dev Fee,just I checked in "Awesome Miner" and I didn't see any extra hidden dev fee pools.. But the firmware is reducing hashrate after some minutes,I think it's happening because of voltage issue. Unfortunately this firmware useless for me..

I'm using a Russian firmware "xilinx-antminer-s9-s9i-1.0.7" for S9 13.5 th and I have got result 16.5 th without any issues with 1600w apw3++ psu. But unfortunately having %7 dev fee,damn this russian guy really made a masterpiece firmware..  if anybody can disable dev fee just pm me.. I can pay for it really..