jakubek160 :
This guys tells you some bullcrap. i5 6600k on stock is capable of running it way beyond what you really need for gaming. 99% cpu usage is not telling you that there is something wrong with your cpu , but it should be both 99% usage cpu and gpu. Problem is with your gpu , especially if it happens in r6 siege. It seems like there is a driver problem. Try doing what I suggested.
I have to assume you're referring to one of my posts. In theory, getting 99% usage out of both CPU and GPU at the same time would be wonderful, but in reality, that rarely happens. In cases where you can come close, it's still not constant, as software code imposes variable loads, especially when there is human input involved, such as gaming.
If the OP is CPU bound, no amount of graphics driver replacement is going to help.
Furthermore, nobody has claimed that either the OP's CPU or GPU were in any way malfunctioning. In fact, from his description, they both appear to be working just fine. I'll say it again. Because i5 processors have 4 cores and 4 threads, they tend to show high CPU usage in well threaded games. This is just a matter of fact, not a malfunction or declaration that there is anything at all wrong.
As bystander pointed out, since the GPU is not the bottleneck, turning settings down is pointless, except to decrease image quality. The GPU clearly has the horsepower to render more demanding settings, past what the OP has stated to be using, without affecting frame rate in a significant fashion.
I stand behind my original answer. The only other option would be to turn down in-game settings that cause higher CPU usage, freeing up resources for the rest of the game engine to put toward the in-game render thread(s). Most games don't offer up much, if any, in the way of settings that will reduce CPU overhead, only GPU, so that is where the OP has flexibility with his current setup. If the OP wants to achieve a higher frame rate, since his GPU is being underutilized by his current CPU arrangement, he can either coax more speed from his current CPU or replace it with a CPU that has more resources and therefore in some games can provide more frame data for his GPU to render.