Thank you both for your comments. I am still trying to figure out what can be happening.
https://ibb.co/kpvgrwThis is my current situation, after trying every power option in my windows 8.1. You can see that after exactly 2 minutes being AFK, mi hashrate drops from 30.5 Mh/s to 22 Mh/s, and returns to 30.5 Mh/s exactly when i move my mouse.
Also I've been mesuring power comsuption while in 30.5 Mh/s and while in 22 Mh/s and both are the same. It doesn't save any power...
I wasn't able to figure out how to change power level options in my GPU (Asus GTX 1070) so, maybe I still have light at the end of the tunnel.
You know, the funny thing is ... your temp doesn't drop. It looks like the card is doing the same work but is being miscounted for some reason. When mine slows, I usually see a couple of degrees drop off of the temp.