I was suffering with stuttering in P3d 2.4, I upgraded my GPU to a GTX970 and had a significant improvement but still some stuttering, at UK2000 LHR I was only hitting 21-23 FPS

 

I installed a freeware program called process lasso and noticed that P3d.exe was set to a priority class below normal? setting this back to normal removed my stutters and FPS now hit the lock that I have set at 25FPS

 

I dont know if I did something to set this flag before or whether P3d comes defaulted at this, anyway its improved my sim immensely so it may be worth checking yourself

 

regards 

Don´t lock your fps, switch it too unlimited. You will get more fps and more smooth.