Since we are on the topic of suspensions, something that is paramount to getting the most performance out of any set up is the ability to transfer motion accuratly and consistently. Before even getting into suspension changes or mods, ensuring you have a stable platform to work on should be priority 1. At the very least these would be torque boxes or subframe connectors. The more power you are planning, the more agressive the driving, or the higher the wheel rates you are planning, the more important this becomes.
XVs stiffening kit is a nice, packaged option for this improvement that can be installed in a completed car with only minimal break down and reassembly work. If you are in the bare chassis stage and want to really step it up and look stock, welding up all the stock, spot welded body seams can also have a major impact on chassis rigidity. Once you get to the "all stops removed", race car on the street stage, then a roll cage with a fully integrated front and rear section is the ultimate in three dimensional support.
