Exhaust, gears, ignition, intake, then and programmer, there is a aftermarket but a limited one; you might even want to throw a supercharger on it, or nitrous after you upgrade the other parts.
I Just got my 03 3.8 mustang and i need more hp. I had money for gt but couldnt afford insurance. So any suggestions where to start?
What are you HP goals? and how much money do you have to spend ?
The Items posted above are all good . You have to take in other considerations when you go nitrous and superchrger though , such as fuel upgrades and rear end upgrades , really depends to on what you want the car to do for you , street ,track those kind of things .
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660.0 RWHP 583.0 Ft. lb's trq. @17.4 PSI
11.584@124.58mph( Old set up)
2002 V6 3.8 liter.
T-5 G-Force Dog Ring
Custom T-80 Turbo built by Delk Performance
you can put on all the bolt ons for much less than that ,UDP, CAI, gears , good dual exhaust will feel pretty nice compared to stock , Heads , Intakes and cam will add more .
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660.0 RWHP 583.0 Ft. lb's trq. @17.4 PSI
11.584@124.58mph( Old set up)
2002 V6 3.8 liter.
T-5 G-Force Dog Ring
Custom T-80 Turbo built by Delk Performance
yea, Exhaust will give you about 20HP or so... UDP is under drive Pulleys, They don't give you more power, but they do free up HP, allowing more to the wheels, but be careful if you have a big system... since they will slow accessories a %, you can get 14HP from the 42% pulleys
Ive been readin around on here and some say exhaust does not give it any hp????? i thinkin bout startin off with CAI and throttle body spacer, maybe new throttle body??
Start with exhaust... just make sure you do dual exhaust... and you have to stay under 2.25" pipes, you will see a lot bigger gain with exhaust rather then CAI
2003 Mustang 3.8 Mustang Looking For More HP, Any Suggestions?? 
2003 Mustang V6 300 HP For Under 2K ? 
