Lag with games after upgrade

[AMDGAmER9]

Hi all,
So I recently upgraded my gpu and monitor, I have very weird fps lag I never had.
My specs:
-FX 6300
-MSI 970A-G46 Mobo
-8 GB DDR3 1333Mhz ram
-Gigabyte GTX 760 Windforce X3 4Gb (Upgraded from R7 260X)
-1 TB Seagate HDD

I was playing on a 18.5" LCD monitor (1366x768)
Tonight I got an LG 23" FHD LED monitor and now I have massive lag, I expected less frames but not dead solid drops.
I tested BF4(Constant 86 fps and every 10 seconds drops to 8fps for 2sec), Cod advanced warfare( spikes between 91 and 38) and far cry 4(runs much better without lag)
My games were running fine before the upgrade???
Can anyone help please??
Thanks!
Oh btw I run everything on High, some settings Ultra and 2X MSAA

 

[RCguitarist]

Did you remove the old GPU's drivers and update the new card's drivers through Nvidia's Geforce Experience application? If not, do those first.

 

[AMDGAmER9]

I found the problem, for some reason there were Modes enabled in my BIOS to throttle my CPU and RAM, didn't know it came on but everything is sorted now!
Thanks for the help anyway!