You have something going on. I run at 4k, on an overclocked Xeon 5660 and a GTX 780. Never below 30. Usually much higher. As much as I hate to suggest it, a clean install of Windows?I don't think I'm doing anything wrong in X-Plane 11 that is causes those times when it dropped below 20 fps, it not often it happens, and usually stays between 20-30 fps in huge cities and 30+ over rural areas and small cities. With the stock Cessna 172 the fps are higher in those same situations. I don't want to lower anymore settings. I already minimized reflection details, disabled scenery shadows, and disabled AI aircraft. Sure I could lower more settings to get better performance but I don't think it's worth lowering more settings. 4k should not stress on the CPU more than 1080p because resolution is all GPU. I also have my CPU at stock settings. I plan on upgrading to an i9-9900k.