I'm going to place this inquiry here because it is the platform I use.  Notwithstanding, the issue may be globally encumbering to pairing Flight simming platforms.  (Note, I've also posted this in LM forum)

"SKY TEXTURES".  

I'm curious as to how many of us have invested and use ENVTEX or REX Sky Textures.  Bear with me.  Lately, I've notice some interesting effects on performance with these enhancement textures(programs).  In particular, spikes in CPU usage when certain sky textures package are in use.  Today, as I write this, I'm experiencing 100% CPU usage and blurry textures despite making any adjustment to the UI settings within P3Dv4.1 (specs: I7 4790K, oc to 4.6 voltage at 1.260- GTX 1080).  

Using Envtex/ENVDIR with sky setting of "Random" I flew out of FSDT KMEM for AS EDDF.  I've experience long texture loading times as I switch views and the CPU spikes and ultimately flat-lines at 100%.  On this flight, under the random ENVTEX setting, i'm seeing a sky set for the first time (in all my flights using ENVTEX/EVNDIR).  Oddly, and to the point, as I continue my track east with the sun setting on my tail and blackness befalls, the CPU usage dropped dramatically to 65% usage. Thus suggesting that the sky, now black, no long contain textures that may induce high CPU usage.    
Now, I love ENVTEX/ENVDIR and by no means am I pulling down the application.  ENVTEX/ENVDIR is not the only time I've witness this.  I had an identical challenge with REX4 which was then resolved by earlier versions of ENVTEX or and the Free Sky Texture Packages.
So I'm putting this out there for us to investigate and mitigate the potential threatening sources(s) so we can get back to flight.
Share you thoughts and experience
thank you
Keino333/usaboy

Way too many things going on to establish sky textures as a cause. P3D and FSX both have a problem at dawn/dusk even with default textures. Some textures may hit harder than others just as certain cloud combinations can bring a system to it's knees.

I think you may come to a "general" conclusion that some textures will use more cpu power than others simply because of resolution, size, etc. And, the system itself will affect those results too.

Vic