flashing bios is totally different from changing the voltage setting in the bios...
anyways, it might require more juice, generally speaking, the general overclocking range only requires small voltage changes while once you reach the dead zone (where you need amazing cooling) you need a large voltage change, .2-.6
I'm not sure. There's an option in my BIOS called "PCI-E overvoltage control" and that I believe gives more voltage to the slot. Some guy said he used the GPU BIOS flash to get a little higher than where I am now. Here's the link: evga 7900gs overclocking - Overclock.net - Overclocking.net
I dunno though, if what your saying is true, then it would make sense why I can't get the core/memory higher.
I think I'll try some of those pencil mods. You need one of them voltmeter things though I think to check what the voltages are, so I'll have to look into that.