I don't like the boost program that Nvidia incorporated with these cards, I use to see my cores go all over the place during gaming and I wasn't having it! Have you tried the K-boost function in PrecisonX it locks your cores(at whatever you oc them to)and voltage to max.
I get better fps this way, than letting the program decide when to boost the cores. If i wanted to run at 1084 core speed I would of bought a 650/660 gpu 

SeanEJohan

I don't like the boost program that Nvidia incorporated with these cards, I use to see my cores go all over the place during gaming and I wasn't having it! Have you tried the K-boost function in PrecisonX it locks your cores(at whatever you oc them to)and voltage to max.
I get better fps this way, than letting the program decide when to boost the cores. If i wanted to run at 1084 core speed I would of bought a 650/660 gpu 

 
Does K-Boost boost at all times, or only when running 3D applications? If not, I might try it. I recently flashed both my 670's to the new 5C Bios, and my cards clocks went down from 1137mhz (stock, 122% PT), to 1110mhz, and my voltages on one card stay at 1.162v rather than the 1.175v that I'm used to. I'm getting about the same performance as before, but these little things are enough to drive me nuts for no reason. 
 
Also, OP, check the performance graph in-game, see what that looks like, To enable this, you need 2 commands:
render.PerfOverlayEnabled 1
render.PerfOverlayVisible 1
Almost everyone I talk to has the yellow line spiking (CPU) like crazy in multiplayer, mine settles down only with Vsync on. Ideally you want both yellow and green (GPU) lines to be even and as level as possible, but that's almost never the case, especially in multiplayer (64 player maps get the worst spikes).

Also, is this the only game you're seeing this type performance in?

See, I get the opposite results with K boost. When I use it, it will not boost what so ever, it just sticks at the factory stock clock on my FTW+ (1006 I think?), even when I try to OC it to 1280 core it doesnt boost. Also setting to performance in the Nvidia control panel makes it run at max core clock until I turn it back to adaptive.
 
Strange though, always wondered if something was wrong in my card or not..

Globally. I usually just use the same settings for every game in general so I just go to the global settings in the control panel.