The stock supplied Forester XT swaybar is 16mm which gives the chassis a characteristic of initial understeer, good for the average driver but not fun for spirited driving or inspiring confidence at speed.
An easy and affordable upgrade is to swap to the 19mm swaybar from the STI, which will eliminate the understeer without compromising ride quality. This is also a good upgrade for the WRX, but non-turbo Impreza’s should also upgrade the front swaybar to maintain chassis balance and handling characteristics.
You need a 20451FG020 (19mm swaybar) and two 20464FG020 (18mm bushings), which usually ship as a complete kit. 18mm bushings are the correct size for the 19mm swaybar to eliminate slop and movement.