At this point, you should focus on longevity. Modifications that increase performance are not wise for a car of this age. Be sure that the car has been properly maintained. If you do not have receipts showing a new timing belt and water pump within the last 7 years, assume that it hasn't been done and make that a priority. Timing belt services will run you ~$1200-1700 and are essential. Failure to perform this service greatly increases the chance of catastrophic failure.