Hey Hotmetal, sorry if you have already mentioned this somewhere, what Make our your Cards?

I have 4 x Sapphire RX480 8GB Nitro+ and two of them have had the BIOS Modded on them from the Mod in this Video:
https://www.youtube.com/watch?v=Mwb67g4skGM&t=356s

I am finding that my H/s can fluctuate on my cards between 130 H/s and 154 H/s per Card, sometimes hitting a total of 612 H/s and sometime down in the 560 H/s

I have a 1600Watt PSU, but not as of yet overclocked the cards,

Just wondering if you have modded your cards at all? Also which variables are you using?

Sorry for all the questions, just want to try get me Hash Rate Stable and Running at the best it can be, (Electricity is also not an issue for me :-P)