I've noticed lately that when flying it looks like I'm flying thru "thick air" or almost an under water effect. If you make a sharp turn, it almost has a rolling effect in the air, kind of a shimmer. Any ideas on what settings I can change?

Change Vertical Sync (Vsync) from 'application controlled' to 'on' in your videocard driver settings, that will get rid of your screen tearing.It was on by default in fsx rtm and sp1, it's off by default in sp2, which may be why you haven't seen it till recently. If you're running DX10 preview though it will never work unfortunately.Cheers,

After further testing, I see this "heavy air" problem only occurs in window mode. It is not there when I fly full screen. Anyone know what this means? Vertical sync did not seem to help.

Vertical sync being on is what keeps it from happening in full screen, but it cannot work in windowed mode on any game to my knowledge because windows itself drives sync control of the desktop. It only works in full screen, where the game can essentially 'take over' your videocard. What you're seeing as 'heavy air' is a difference between the frames per second that the game is able to display (or is locked to) and what your monitor's refresh rate is. Think of it as two sine waves with slightly different periods. Some of the time they will synchronize most of the time they won't. The wavy horizontal line which travels down your screen now and then, or during turns, in windowed mode is a result of that desynchronization causing a kind of image lag. If you run the game windowed you'll just have to put up with the screen tearing I'm afraid.http://en.wikipedia.org/wiki/Vsync