Video card, or CPU?

[Airspeed]

Followed all the instructions on using Afterburner.
Overclocked the graphics card from 830MHz to 850MHz. FPS in the test set (NOT FSX), improved from 36.2 to 37.1
Overclocked to 890MHz, and the DPS went all the way up to 37.9
At 830, GPU was 66°; 850, 73°; 890, 74°.
Tried upping CPU from 2004MHz, screen froze on scene 12/26.
Reverted to CPU 2004, but at 890 on the GPU, I lost video signal. Decided that overclocking wasn't going to work for me.
All reset to default.

[Airspeed]

I tried a different approach last night, switched off HD cockpit interior.
If you imagine that you're in your own aircraft, which you gave a quick slap of paint to tidy it up, FPS jumps from 9 to 20.