Ryzen 5900X strange CPU Usage, low FPS

You know, I wouldn’t complain, if it is normal, but others, with the same setup, the same aircraft, the same setting and the same airport, get nearly the double FPS as me.
If I got 33 FPS STABLE, it would also be okay, but what I tried know:
Approach LOWK (no photogrammetry even in the area), Approach with the B787-10…
Max Frames are about 30 to 33, droping below 20 during approach.

Just tried it again, hit 40FPS… but only with the Extra ^^

5900X, 3090, 64GB@3600… That couldn’t be normal

BTW:
in Thunder Storms the 3090 is limiting ^^