Thanks for everyone.
I increase voltages a little, 2.0v instead of default 1.8v
Now the 4 sticks is running at 391mhz 5-5-5-16 CR2. I'll test the stability for sure.
CPU 2750mhz, memory set to 667mhz divisor what results 391mhz in my system.
Increase a little, is by 0.05v
2.0v is way to much.