good tires, good fuel, and seat time.
But since that's the most generic answer ever, I'll also throw in:
1) Weight savings. The 986 is surprisingly heavy given it's size. (~2900 lbs stock)
2) Camber. The rear factory limit is about 2.5-2.7 degrees, which isn't bad, but the front is less than 1 degree.
3) Short shifter. This one, specifically:
https://uniwerksdesign.com/product/bens-porsche-996-986-short-shifter/ Amazing quality, and lower price than most others.
4) Thermostat. After a couple of hard laps, we noticed the temperature creeping up. The car never overheated, but we figured if we can keep it down, we could. You can get a 160 degree thermostat, vs the 180 degree stock.
5 A full exhaust, if only to let the M96 sing her song.