Welcome to 986forum Kaili. It seems you play this game very well.
You already have a dozen Boxster owners at the ready, to look after your every need. Bravo!
Ok so lets break this down a bit...
You have one of the finest German sports cars ever made (2003 Box S) and you have some of the best mountain roads in the western hemisphere out your back door. It doesn't get much better than that does it?. So now what???
The fun stuff:
Making the driving experience even more exciting. As others have suggested, bolt on mods and performance add-ons are really quite weak for this car and will most likely leave you unsatisfied at best, or cause problems at worst. Gentle suggestion, leave the motor alone for now and really get to know her a bit. If you still want to tinker after a year or so, have at it.
So if not hp add-ons, then what? The secret sauce with these cars really is all about high performance tires. The difference is amazing! Most new Boxster drivers have no idea how a fresh set of excellent rubber will transform your car. I drove on lame A/S tires for two years before I figured this out and I couldn't believe the difference it made. Like adding 100 horsepower in terms of excitement. Don't wait, do it now. Find a good used set of takeoff Boxster rims on craigslist for around $400 and add nice fresh high performance tires all around. You will absolutely love it. If you choose wisely you will spend around $1k and it will be the best money you can spend on this car. Save those All Season minivan tires for winter snow days.
Ok now the boring stuff:
To get the most out of your car, change the oil and filters every 4-5k, change the brake fluid annually, warm it up gently when cold, and drive it like you stole it with some serious canyon carving at least once a week. It keeps her healthy and happy.
You have my 2c. Don't be a stranger.
