If I understod the tweker correctly it did change my CFG file? If it did there was no chamge in performance.
You should at least noticed a change on your actual *settings*, at least those that you can tweak with FSX normally. If you don't see any change, it's possible you are still using your original FSX.CFG ? It's unlikely that site would propose you *exactly* the same settings you already had.
I have also used the NVIDA Inspector to tweek the graphic card. I used a setting sugested by PMDG (before I discovered the problem with KORD).
Try to reset your video driver with all default settings, and see if it changes anything.