Question GPU not utilized in GTA V

[Rivstar]

Hi, I have a 12900k and 3090ti and I often get sub 60 fps in GTA V. I've spent about 5 hours troubleshooting things, i've tried absolutely everything i could think of. I've narrowed down the issue to the fact that my GPU refuses to utilize it's self above about 43%, under load it stays around 37-43%. Other peoples 3090ti gets vastly better performance than mine in gta. There is no bottleneck with anything, my cpu and ram are fine. I have changed vsync and gsync settings on and off on my monitor, nvidia control panell, and in game settings. I'm wondering if this is a problem with gsync being on somewhere or something. This issue only exists with GTA V, every other game I can play perfectly fine with no issues and get the expected framerates.
Here are the things I've already tried:
changing every in game setting (the fps remains about the same regardless as to any setting. at 720p and at 4k I get the same fps, high or low settings I get the same fps.)
changing countless settings in windows like power delivery settings to maximum
changing countless settings in the nvidia control panel
changing monitor settings and trying another monitor
updating motherboard, cpu, and gpu drivers
changing my operating system from windows 10 to windows 11
changed all the gpu overclock settings

I can't find any similar issues online and its a little frustrating having sometimes unplayable performance due to to regular sub 60 fps 1% lows. I'm very competent with technology myself and have already had half a dozen people help me troubleshoot and absolutely nothing. Maybe there's something simple I've just overlooked, any advice would be great.

 

[rgd1101]

full system spec? include brand and model of the psu

cpu/gpu temp and usage during the game?

 

[Rivstar]

https://uk.pcpartpicker.com/b/fwz7YJ
CPU utilisation is 15-25% which is consistent with other games. Temps are sub 60 degrees.
GPU Utilisation is as I said 37-43% and 60-70 degrees. nothings thermal throttling and theres no hardware issue, my system runs as expected with every single game except gta.