Often lowering your clocks a bit helps
Using -rxboost option and amdmemtweak helps a lot.
Thanks for the advice. I'll definitely give these tweaks a try.
You should start looking for a new miner, because in probably 2 weeks it will be impossible to continue mininig ETH with Claymore... and for the history it seems no update will come. You can have a try to lolminer that can be combined with the utilites of AMDTweak to let you this extra 1 Mhs with the -REF 30. If you are going to mine other Ethash algo except ETC/ETH you can continue with Claymore...