#1 is tire pressure! Go with 35 front, 34 rear as a starter.
#2 is the STI anti-roll bar. We didn't replace the brackets, just the bar and bushings. If the brackets bend I'll replace them but I have to assume that the taller Forester brackets are matched to the suspension geometry of the Forester vs. STI.
These two mods did a great deal to correct the wallowing feeling.