Solving a Stuttering issue in FSX on Win8.1

I know I may be behind the times here but I've searched everywhere to find a threat that speaks of the best ballance in tweeks for FSX running on W8.1.  I know about the joystick issue and have the registered copy o fFSUICP so thats not an issue, what I'm getting now is periodic stutters that last 3-5 seconds periodically, almost like the windows resourses are being sucked up durring those moments.  My specs are as follows:

Intel Core I7 3.8Ghz

8G mem

Nvidia Geforce GTX 660 ti

Windows 8.1

Standard FSX with Accelerations

PMDG 737NGX

PMDG 777

PMDG MD11

ORBX 

Any help would be greatly appreciated, thanks