I found the post! It is a good read:
For everyone wondering why they can't get phenomenal performance as they expect with their high-end systems:
http://jetlinesystems.com/performance.php\
There is a lot of conversation about this FSX-performance stuff. Where a $1000 gaming rig may be able to play BF4 on high settings at 60 FPS, the same wonderful rig is terrible on FSX with medium sliders and leaves you asking why, and there are many reasons.
1) FSX is a Simulator: Being that it is a piece of software that outputs simulator-grade flight; it requires many complex CALCULATIONS to keep everything realistic, from aircraft-weather interaction to aircraft systems and response to various things. These calculations are extremely CPU intensive and have almost nothing to do with the GPU, which brings me to my next point:
2) FSX works better with Intel CPUs: I don't understand this 100% but I have heard from a reputable source that Intel's architecture (pipeline?) on their CPUs are much better for doing these calculations than AMD's CPUs. I'm not fanboying: Intel CPUs just wrok better with FSX than AMD CPUs. And the farther the generations go on, the better they will be able to handle FSX calculations.
3) FSX is poorly-programmed: The programming is not made to efficiently utilize all aspects of your rig; it does so quite poorly. It can't place those flight calculations all over the cores for the calculations are single-threaded. Also many things that should be graphically dependent are CPU dependent.
4) FSX is not graphically focused: GPUs play a small role in the FSX world. They need to render frames, models and locations at default, but that is it mostly. A high-end GPU only comes in play when you bombard FSX with graphic mods such as ENB, textures and good looking airports. nVidia architecture is best for FSX though, but SLI is terrible for it puts more of a load on the CPU everytime you put more GPUs in. GPU=NO BIGGIE
So what now? Playing FSX at 60FPS constant with all sliders at high seems impossible! Want to know why? Because it basically is. With all of the reasons above, it will be a while before we can achieve such a feat. Unless you have the means to overclock the Haswell-E processors to 7+GHz, you won't be near your BF4 performance.
FSX does have problems with FPS. The root of the problem is not your GPU. Look at the link to see information about FSX-RAM correlation (High MHz, low CL#). $1000 CPUs are the best we have. SSD is the greatest upgrade for FSX when it comes to storage; it works wonders.
The best rig for FSX:
4th gen. OC'd extreme Intel processor
SSD for storing everything FSX
RAM with high memory processing power (1866MHZ+) and, more importantly, low CAS Latency (CL8-)
For things to look good, a latest-gen GPU from nVidia (760+)
I stand by my i7-4790K reccomendation. I do not reckon your current set-up will suffice. And the highest edition (deluxe) goes for about $20, so I would get that.