I seem to have solved the problem for the most part on my legacy. I was having the problem where it would stutter at certain RPMs when cruising or going up small hills. I found this thread http://legacygt.com/forums/showthread.php/stutter-studder-hesitation-etc-198070.html?t=198070
Basically the theory is that a resonance builds up at certain RPMs in the fuel injector line which causes one of the injectors to get starved of fuel and then that cylinder runs extremely lean. I followed the modification suggested in the thread above and replaced one fuel line with a longer line.
It seems to have worked well for me. I can still get the car to stutter, but it is much less common now. I have driven about 100 miles since replacing the tubing, and have only had it stutter maybe 3 times. Before the replacement, my car would stutter more than 5 times every time I drove.
As a side note, there are some compensation tables that subaru tried to use to "fix" this issue which you are supposed to zero out when you do this mod. I have not got a chance to do this yet, so hopefully my stutter will further improve when I do that.
It may not be the fix for everyone, but it cost me about $20 in fuel line and clamps, so it is worth a shot.