does it only do it under load ? If so the springs may be old, mine came with spring assistors in to help, if you have the self leveling units in the rear they could be on the way out,
Pedders do a lifting kit gives about 2" i think, new shocks and springs all round, may be worth looking at www.forester.org
The guys in the states have loads of info on it, you can also change the subframe spacer blocks to give more room but it's a big job