Windows 10 throttling ethernet speed

[exooo]

I should be getting gigabit speeds, when I test with speedtest I get around ~140mbps, fast.com shows 300ish, sometimes 400.

My NIC is set to 1.0 gbps, my network card is not the issue.

I tried a new windows installation on a spare SSD drive, the speeds were instantly 1gbps without problems. This is an issue with something in my windows.

I don't want a new windows installation unless it's 100% needed.

If you need any other info, let me know.

I feel that this is 100% a problem within my windows installation.
I feel like it's throttling, as the tests are very stable and feel like they don't want to go over a certain speed.

 

[exooo]

Solved this issue.

I used the SG TCP Optimizer long ago (when my speeds were 150/15), I reset to default windows settings and now my speed tests immediately hit 900.