I would expect about a 5-10HP gain from a borla cat-back system. A chip would probably get you 5% or so gain in HP and torque. If you already have the "sport" package then don't worry about it but otherwise I would recommend you get some more aggressive rubber on the car. Tirerack is a good place to browse around and learn what you might want. As far as computer tuning, whether your car's engine management computer is E-prom based or Microprocessor based will determine whether it is easily chipped or not. That is something that varies within models and model years. If you have any other questions or need help finding out feel free to email or post back.

Lee