This is my first post in the avsim forum. I have the exact same issue. In Prepar3d V2.2, I didn't have any issues flying through clouds. I've tried a few tweaks of my own without any luck. I've read several articles and still no luck. This article matches my exact issue.
Simulator:
Prepar3d V2.3
CPU Specs:
I-7950 @ 3.01GHZ
12 GB RAM (DDR3)
750Ti 2GB RAM
Addon's
REX4
REX Essentials + Overdrive for weather engine
I use some photoreal scenery I create with FSEarthTiles
V/R
SloopJohnB