guys i have E8500 Q746A363 and i can't set 4.3GHz with less then 1.45v

i have a friend that haves same batch and does 5.1GHz or even more with 1.47v (at least that's what he says)

i might be missing something here...

help me out here, might be NB Voltage; GTL; DRAM frequency; Vcore;
SB Voltage; mem Config (i don't know)