RE: big frame rate problems
I don't think your processor and graphics card are really up to FS9. With your system, I think you will need to have many of the sliders towards the left.
I have had a bit of jerkyness since installing SP2 and think it may be something to do with soundcard drivers which I am told are installed within the service pack.
Did a clearout last week and re-installed FS9 with improved results. Some of the addons must have been having an affect. Still have some slight jitters when ATC speaks though.
Q9550 @ 3.78 GHz with Gainward GTX570 1.25 Gig DRAM
4 Gig DDR2 RAM - Windows 7 64 Bit
Resolution 1680 X 1050 X32