Upgraded graphics card but get lower fps?

I should start from the beginning I guess. So I got a AMD Sapphire 290 Tri-x to replace my way old AMD HD6850. So I did a clean removal of the graphics drivers. Switched from windows 7 to windows 8.1 and installed everything. Altho now I get lower fps in cs:go for example. And I can get weird fps drops. I really don't get why this is happening. Tempatures are all fine too. 

CPU: Amd a10 5800k (Yes I know APU but I got it REALLY cheap)
GPU: Amd Sapphire 290 Tri-x.
Ram: Ballistix sport 1600hz 2x4gb.
Mobo: Gigabyte F2A85X-D3H.
PSU: Corsair CX600.

After the recent updates Csgo's fps are all odd, to say the least. Valve is working on it but I dont know when they will fix the issue.  For example my 970 with 8350 will only run at about 150 fps!