It seems that if it was designed to use 2.0 specs, it would preform at the slots specs instead, go figure. Why would you expect anything else? Just like USB1.1 and USB 2.0. You cannot force the slot to act like a 2.0 slot if it is not designed for that.
I was wondering if a PCIe 2.0 video card would work in a PCIe x16 slot? If so is there performance lost?