hey everyone i have just bought a 2003 subaru impreza ts with the 2.5l.

Full tune up is always recommended to be done to a car when you get it. Cheaper mods would be a CAI and exhaust, that will open up your car's breathing.

Honestly, there are not a lot of mods that you can do with this motor. If you get really crazy you can spend thousands on head work with cams and tuning, as well as doing a header and full exhaust. This route is very labor intensive, and very expensive. You can make it handle very well with some minor additions like sway bars, a good spring/strut combo, and a nice light set of wheels and tires.

Both trevor and Ryan are right. although I would skip over the CAI (cold air intake) they almost never give you any more power except on specific cars with badly designed stock intakes (of which this is not one) and the power gains are very negligible (3-5hp). a cat-back or better yet full exhaust (exhaust and headers) will do somewhat better and will add somewhere in the neighborhood of 10-25hp depending on the car (I dont know the specs for this car). be careful to stay with a small exhaust size such as a 2.25in or 2.5in at most on an NA car and 2.5-3.0in on a turbo setup, it will not need more than that in either case and too big will cause a lack of backflow which is needed for a car to function at peak power. Like Ryan said though, I would work suspension and brakes first and learn to drive it well, that will make you much faster than a few bolt ons. good luck with it.

thanks guys these are all answers.

Before power, you need the control... brake and tires !! It's possible to change for better parts from a WRX. Personally, put a lock diff. at the rear of the car, it will change positively how they response to us.(but you need to change trany to for good gear ratio...) (sorry for my language/writing, speak well only in french)

im thinking about picking up a set of wheels and tires in the spring, as well strut tower braces and larger sway bar and energy suspension master bushing kit, engine mounts, transmission mount, and shift bushings.