When should you upgrade torsion bars?

As TrailBeast mentioned sub frame connectors made such a big improvement to handling (cornering) and took out the flex in the body. By saying that just driving down the road and going over some uneven road with some dips where as before you would feel the car flex over this section of road where as now the car is more stable and tracks really well. Under load is pretty good as well as the car doesn't buckle, PST is the brand name of the Vendor selling the bars.