I have major mods to the rear of my car and I can say that your first add-on should be a rear tower brace. This eliminates the "fifth spring" and lets the suspension do the work it was designed to do. My bar is a custom piece with a 3 point weld on mounting arrangement. It made a HUGE improvement! I'm running 19mm front and rear bars with no squeaking, rattling, etc. My car is very neutral in the handling dept. It's not necessary to add a big rear bar to reduce understeer. There are many other factors which can add oversteer/reduce understeer. The existing, available sub frame connectors are generally a waste of $$$ as they strictly address chassis flex. Our cars are strong in bending. What does work is a proper X brace. Cornering loads are almost exclusively torsion loads, and this is what an X brace cures. I'm presently designing an X brace to really tighten up my '95.
