I would suggest one of the tuners for it. A Diablo Predator (if you can find one), or one of their new Intune's. The included tunes will give you a nice bump in power, and allow you to firm up the shifting, and you'll need the tuner eventually if you want to start doing internal engine upgrades or FI. :bigthumb:
A good Intake and exhaust are good places to start also. You won't get a lot of HP from those, but will probably pick up a few mpg's, and they'll come in to play with other upgrades. They add on to the cumulative effect of upgrades.
If you want more performance, definitely start with a tuner. No matter what you do afterwards, the tuner will optimize performance. We have lots of goodies to choose from. If you'd like, we can work up a nice package for you