Meanwhile i got it at 3.9ghz at 1.5v but at 1.46v at load.
Highest temps using core temp was 48c.
I runned prime for 30min on the blend option without errors (should i use one of the others?)
When at 3.9ghz and 1.48v i got an error at one core after 12min.
I dont think i will go an give it more volts.. well 4ghz is a nicer number though
I still would like to get some info about the correct voltage of the cpu/nb.