But some complain about single digit speed losses so for those, yes.
I can't find the articles about PCI 2.x versus 3.x and 8 or 16 lane changes so I'll peg it at single digit performance change most of the time.
I don't see any reason not to move the card. Is there a reason?
So, it turns out that I've had my AMD Radeon Vega Frontier Edition plugged into a PCIe3 x8 slot the entire time have had it, when I COULD have installed it in an x16 slot. I primarily use the card for GPU assisted video rendering and cgi rendering. Am I losing any major performance on this particular GPU by only giving it 8 lanes, assuming that my CPU/motherboard have the bandwidth for up to 16 lanes for my GPU alone?

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic