On the other hand, with NO$Zoomer can play to 95/100 % (nocash render) and 85/95 % (opengl render) of perfomance... I love No$Zoomer (NO$GBA included... AR codes necessitated).
Hm... having said that, have you tried disabling "Advanced Bus-Timer" in Emulation Settings? 'Cause it's turned on by default and can cause massive lagging.
Simply go to Config > Emulation Settings, then de-select the box next to "Advanced Bus-Timer".