Just wanted to share this
http://www.venetubo.com/fsx.html
It automatically configure your fsx.CFG the best way, according to your system spec.
secondly and the most important advice, is to download FPS limiter 0.2 (http://rapidshare.com/#!download|487l32 ... .2.rar|166) and use it instead of fsx built-in fps limiter
with a P9500@2.87ghz and a 9800m GS 1GDDR3 i've easily won 5 to 10 FPS
Don't forget to put your fps limitation in fsx to" unlimited "
the other part is greatly described here :
http://www.simforums.com/forums/topic29685.html