With help from a lot of people, I was able to OC the stock ram from lenovo 5200MT/s (42-42-42-42) to 6000MT/s (36-37-37-34). FCLK raised from 1733 to 2100MHz.
I have learned that tRCD is highly dependent on chip binning. Unfortunately lowering it anything below 37 results in errors with 2mins in TM5.
I was also unable to decrease tCL further. I tried raising Vdd upto 1185mV but still no luck. TM5 errors within 2mins.
I have now settled with these timings Vdd at 1150mV
The performance increase in CPU bound games is insane. My FPS in dota2 and even during extreme scenarios it doesn't dip below 170fps.
TM5 absolut 3hrs no errors
TM5 extreme 3hrs no errors
Prime95 ran for 5hrs no errors