mine isnt stable at 4 ghz below 1.35vtemps are similar to yours
Try enabling Cpu Enhanced Halt (C1E) first.
Not sure about the other one.
You don't have to disable it to overclock as it should go to full power under load.
Hmm, could be something working in the background making it fluctuate causing the volts to stay at maximum.
I seem to remember there was something posted a while ago about some settings you can alter to set a minimum and maximum Vcore on a Gigabyte x58 UD5 with a i7 920, don't know if this will apply for your cpu and board though.
Will have a look for it and post back.
Im using the Gigabyte Motherboard
Cpu Enhanced Halt (C1E) = Disabled
C3/C6/C7 State Support = Disabled
do you think I need to enable both of those then as I thought when oc you need them disabled ?
With such a modest over clock I would certainly have them enabled. I tend to only disable when I am going sub-zero and really pushing the over clock to the limit.
As to how to set the max voltage with the UD range of boards - just set the voltage in the bios it is really easy to do. If you get stuck post here and I will walk you through it.
Think this may be V-drop or whatever it is called, try raising Vcore up a notch to compensate.