Hi there.
I have the same "problem" here. In fact I was about to start a new post to ask for help.
In my case I've tried almost everything that this (very good) article suggests:
https://graphicscardhub.com/low-gpu-usage/
Here are my specs:
Intel Core2 Quad 8400
4gb RAM DDR2 800MHz
GTX 460 768MB - EVGA OC edition
Intel DG41RQ Mainboard - Chipset G41
I now its an old PC and I'm thinking about upgrading, but I'm still having fun with this.. lots of "old" games to play..
Anyway, I have two monitors, one that's 2560x1080 and the other is 1440x900. When I play I get the same fps on both. The only thing that changes is GPU usage that increases, but it stays below 95% all the time.
Games that I've tried with similar results:
Tomb Raider 2013
Metro 2033
Hitman Absolution
GTA V
Here's a GPU-Z screenshot
View: https://imgur.com/a/BCwPq90
The only thing that I found strange is that my GPU reports the BUS interface as 8.0 1.1 and not x16 2.0 as it should. I know about power saving, but hitting the stress test (?) didn't change the bus interface speed. I'm pretty sure that is not the problem, but I'm far from being an expert..
Here's a screenshot of in-game using MSI Afterburner
View: https://imgur.com/a/a35xTtI
So far I've tried everything I could, even changed to older driver version, measured my PSU voltage, disabled HPET..
Thank you all for the help.