There's not really any "fine tuning" that can be performed on this car. The engine control module handles ignition timing, injection duration, etc. Other than gapping the spark plugs correctly and insuring the maintenance items are addressed, there aren't any adjustments necessary to maintain performance. Timing chain stretch, carbon build-up, and minor compression loss can cause performance to decline over time. Fuel quality can also contribute ( especially when fuel prices are high ). I would try some injector cleaner first. Good luck