Do I have to "flash" an NVIDIA GTX 10XX (1070/1080/1080ti) to get it to use PCIe 2.0 on a Mac Pro?
It appears that a standard GTX 1070 Founders Edition uses a link speed of 2.5 GT/s (PCIe 1.0) even with the latest NVIDIA Web Drivers:



The GT 120 I have sitting next to it has a 5 GT/s link speed (PCIe 2.0):



So I guess that answers my question.