OK, so I got a Gigabyte z87n-wifi running bios version F2
I have already checked it will boot with F2 bios and G3220 CPU
I updated the Bios directly to F6 then rebooted back into the bios.. No setting changed yet.
As all went well, I put in the G3258 and tried to boot it up. It now spins the case fans for 1 sec and stop, repeating itself endlessly... After i swapped the G3220 back in, it kept on doing that....