hello guys, I looked in various forums but I could not solve the problem. I have an i7-10700K, rtx3060Ti, 32gb ram and am constantly limited by my cpu. I have the lod at 100 (among other things I don’t know why other people with a lower gpu manage to have it at 200,250 when I then septum to 200 in large airports I have a few fps like 23.25. 
I am limited by the cpu I have good fps but my gpu is at 30% and I would like to exploit it all.
Take every “I run the sim at such” with a grain of salt, what some fail to mention is they do this with no traffic or photogrammetry or other settings in what many would find unacceptable.
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Also, GPU utilization in Task Manager is not a good way to tell what your GPU is doing. Keep in mind that the CPU is in charge of the pipeline, and when it says Mainthread Limited it means the CPU is working harder than the GPU. It does not indicate there is a problem. Your best bet is to set your resolution to 1080p and select High-End PC preset. Turn on Vsync for perfect visuals. Turn off the FPS counter and never worry about it again. I run this setup with my i7 11gen and 3080Ti. 
I use msi afterburner to watch gpu performance. Anyway Thanks for the advice!
Following this topic post helped me resolve the same issue you’re having. I’m not saying that it’s definitely the solution, but maybe something that you can try and see if it makes a difference. My spec is i9-9900K, RTX 2080 Ti, and 32 GB RAM. My sim was limited by mainthread and it was running at around 10 fps all around. Once I tweaked my BIOS according to this post, I got 30 FPS from that point on.