Your bug look a lot like mine!!!
You can begin by simple adjustment on the torsion bars( a couple of notch),use some good shocks such as KYB, or better ones such Koni, Bilstein,or adjustables Spax.Combine rear anti sway bar such as sway away,or better adjustables such as Whiteline.You can go to german bushings, or urethane,better ones Energy Suspensions.
Also can go to rear adjustable spring plates(sway away),or 944 adjustable ones.
The final stop are coilvers,recomend special spring plates also.You can go to Eagle,Remmele or MBT(I have MBT,awesome looking).Do not know if KAW produce ones?
If go coilovers recomended are the Kafer cup braces,5 bars better yet.
I just fineshed my rear suspension MBT spring plates,Remmele Bilstein coil overs, 951 rear anti sway bar, 5 bars Kafer cup brace on 951 aluminum arms.Just drive it a couple of minutes on the street.Things are looking promising!!!
Onix