Right click on desktop => AMD-Catalyst Control Center (CCC) => Performance => AMD Overdrive => remove checkbox "Enable GraphicsOverdrive" => done
Got me 3 brand new grey hairs till i found out what was wrong
Those "OverDrive" tuned the card down and "re-adjusted" my mining settings... *AAARRGGHHHhhhh...*
And as i wrote above: every vendor has its own "sweet spot"... not every time is more = more hashes
I guess I never turned it on. When I went in there it first asked me to accept license agreement, which implies I never used it previously.