i'm guessing they are using 14.6 drivers which increases the hash rate of x11/x13/x15 etc. I couldn't get 14.6 to work as it kept crashing my comp, no matter what settings i put in the .bat. Probably because I have undervolted my cards.

So, a work around was to stick with 14.4 drivers and then copy the opencl drivers from the 14.6 RC2 release into the sgminer folder. This increased my hash per card from 2.2 to 2.5 - nowhere near the 2.9 that Bojcha is getting but I would suspect that they have not undervolted.