Already posted this in the 'Anyone Know Of A Good A330 Add-on?' thread, so forgive the double post. Figured it would get more attention and help more people if I just made a whole new thread about it. So, I'll just copy and paste.
I found a pretty good solution to improving framerates. It's not original, but apparently not too many people know about it. One 'word': DXTBmp.
Download that program (probably Avsim, or just try Googling it, sorry) First (and you only need to do this once each time you open up the program), go to Prefs and uncheck 'Include Mips.' Then, open up each texture, one at a time, and save as 'DXT3 with Alpha.' Do that for each texture file, or at least all the major ones, and you're set.
Try that and it should work. Any questions, and just shoot me an email. Actually, you can simply check out this link and learn exactly what I just told you: http://forum.projectopensky.com/index.php?showtopic=8128. A link to download the program is also included.