It doesn't always work but it does on a lot of systems. Instead of forcing a frame rate it lets the sim decide.
There is one other thing you should try. I have used it for ages and it works for me. You only do it once and that's it.http://www.venetubo.com/fsx.html
This inspects the CFG file and sends you a revised one based upon your hardware. It also includes a link on the results page to their own excellent FSX frame limiter (independent of the FSX one) program which you simply use to run FSX in place of the normal shortcut. (Please note that the location you extract the frame limiter to is where you must keep it so I suggest you extract to the place you would normallt run FSX from.)
The tweaker plus the frame limiter produce impressive results. Read the instructions very carefully! Your original CFG file is not within FSX but is found in (<main computer drive>/users/<yourname>/appdata/roaming/microsoft/fsx) There may be 2 cfg files one in lower case and one in upper case. It's the one in lower case you replace. (hover your mouse over it and it's a CFG file not a text document).
Worth a try
IL2, FSX, ROF, SOW, Cliffs of Dover...
Vista Ultimate 64bit. Core2Quad9550 @ 3GHz, Nvidia 560Ti 1GB @ 1920x1080P, 4GB RAM, Creative SB X-FI