You manually set your voltages when you overclocked yes? you didnt leave it on automatic did you? What voltage and clock are you running? and have you disabled intel speed step and / or C1E? (all this can seriously affect your idle temps)
That said dont worry too much about your idle temps (unless of course they are ridiculously high
) , its your full load temps you need to worry about.
Get yourself the latest version of Real temp
Real Temp - CPU temperature monitoring and some software that will push your CPU , Id recommend Prime 95 or if your feeling daring Intel burn test
Stability / Burn-in - EXTREME Overclocking
Run real temp alongside Prime 95 for a good hour , take note of your max temps on all four cores and report back here with them
