I despise my GTX 970. It's EVGA, for what it's worth.
In just about any game I play, my FPS goes from ~250 to ~60. It lasts for about 5 seconds, and it happens roughly every 15 seconds. It makes it a hell of a lot more annoying if you're playing on a 120/144hz monitor, too.
I've seen a lot of people have this issue, but Nvidia seems really stumped about it. The part that's even better about this that I bought the 970 a couple months back. After realizing how shitty it is (and it was past the refund window at this point), I upgraded every single piece of hardware in my computer except my SSD. I formatted, got everything set up, install a few games, and I have the exact same problem with an entirely different computer.
The Nvidia customer support has been less than helpful, with stupid fucks saying shit to me like "oh, well 60 FPS is actually quite acceptable."
lol?????????
I didn't have this shitty problem with any of the older video cards I've tried. I could just use my old video card in the meantime, but my old video card doesn't run Payday 2 that well.
And when I mean any game, I really mean just about any game in any scenario. CS:GO, TF2, Terraria, Payday 2, etc. I could be on the main menu and I would still get these FPS drops. It's pretty fucking bad. The only game that I've seen it not affect is Quake Live. And that's really worthless because a video card from 2001 could make Quake 3 / Live run at 125 FPS.
You could buy it and see if it affects you too, then just return it if it does. I was pretty busy when I first bought it, so I didn't really recognize it until it was too late. So, this fucking sucks for me.