Sorry to hear you are still having issues. I would suggest trying to find a new ShooterEngine.ini and replacing your old one. Not sure if you have tried FPS configs yet, but if you would like, I will be happy to send you my shooterengine.ini and you can replace it with yours to try it for yourself to see if it works a bit better.
My ShooterEngine.ini: http://www.mediafire.com/download/1xh2835rvbttlxt/ShooterEngine.ini
First, keep your old .ini in case you want to go back to it! A common way to do this is to rename your current “ShooterEngine.ini” as “ShooterEngine.ini.backup”
After renaming your old file, place my ShooterEngine.ini or the one you found into this directory: C:\Users\YourUserName\Documents\My Games\UnrealEngine3\ShooterGame\Config
Once you have my .ini in your directory you may have to make a few changes. The settings in my file are specifically for MY computer, so make sure that these settings all match your preferences and system specs .
ResX= (resolution width)
ResY= (resolution height)
bSmoothFrameRate=True (Change this to =False for uncapped)
MinSmoothedFrameRate=X (X to what you want your FPS capped at)
MaxSmoothedFrameRate=X (X to what you want your FPS capped at)
MinDesiredFrameRate=X (X to what you want your FPS capped at)
MinAllowableRefreshRate=X (X to what Hz your monitor is)
MaxAllowableRefreshRate=X(X to what Hz your monitor is)
After you make all the necessary changes, save the file making absolutely sure it is named ShooterEngine.ini and start up your game. If you want to make absolutely sure that nothing changes on startup, you can save the document and right click on it, select properties, and next to “Attributes” check the box that says “Read-only”
Later if you don’t like mine, delete my file and just go to your file to delete “.backup” from it. Now it will read ShooterEngine.ini once again and you will run on your old config.
Worst comes to worst, delete the ShooterEngine.ini all together and run the game to start completely fresh. This way you know that you have an absolutely up to date config.
You may want to refer to this article as well in case you have any further questions:
http://www.crossfire.nu/articles/view/id/990/page/1
Sorry for the issues, I have been there many times with many games. Really hope this helps, wishing you the best of luck!