Bus that connects GPU to CPU

Is this the PCI-E bus? Can overclocking this bus allow the CPU to send instructions to the GPU faster?

Overclocking the PCI-E bus isn't really recommended as it can have adverse effects on SATA drives with data corruption and whatnot, although I have heard anecdotal claims that a moderate overclock can give added graphical performance. I usually keep mine locked at 100mhz as overclocking the PCI bus could bring negative system-wide effects (especially with SATA hard drives of course) on AGP systems.

Some guys clock PCI-E pretty high, around 120MHz. I haven't played with it much, but I suspect that some SATA systems get clocks from that bus while others might not. Try it and see if you like. If something bugs out, clock it down.

I'd suggest using a spare drive to test it though, it'd be a shame to lose all ur stuff

This is true. If you have a spare, just image the current boot partition to the spare and boot from that, then corrupt it all you want while the other one sits in your case waiting to be hooked back up