Im searching for a 03 Impreza 2.5rs and when I get one I'd like to know some small inexpensive thing I can do to boost horsepower and make it an all around better car

Get a Bugeye WRX if you want power in that bodystyle.. It's better you buy that now while your still looking than buy a '03 N/A if your looking for power. They are pretty much the same car otherwise.. 2002+ ECU's are adaptive and anything you do will be learned around. You can tune them with Rom Raider but nobody does it anymore because theres nothing there. You can't add a turbo without a full swap since the ECU will figure it out and adjust in the oposite way

but you CAN make it more fun to throw around corners - suspension and braking upgrades will do that.

 

and shedding mass is good - lighter rims, lightweight crank pulley, lightweight flywheel - all helps it spin-up quicker and accelerate a little faster. take out the rear seat if you never have passengers, leave the spare tire and tools at home if you can always call for help.

 

11lbs mass = ~1 hp

 

4 pounds off rotating mass = ~ 1 hp,

 

it's more fun to drive a slow car fast than a fast car slow.

Haha indeed it is more fun yeah I had already thought of all that small simple ththings to help I was wondering more parts I'm not exactly a car noon but not an expert by any means course everyone knows put a turbo and better cool air intake system but what else can I do and as for the comment on getting the wrx well one just the Impreza is cheaper I'm not made of money but I need a car soon so I'm getting one of those as for 2 I don't know why but I've always wanted to take just an Impreza and make it better then newer sti's(over a long period of time)

stock intake IS cold air - changes to it 'may' make more noise, but can also cause issues with the air intake sensor.

 

exhaust 'may' get you a pony or 2, unlikely more than that, possible zero power increase - soobs breathe well from the factory, BUT a cheap way to get more sound is a muffler delete with a tip turn-down. check youtube for examples.

 

rims are pricey, but you get to personalize the car and, if lighter, free-up some power for acceleration. perrin crank pulley is under $120 or so, much lighter than stock. Someday, the car will need a clutch - save your money for a little lighter flywheel.

 

look for a local SCCA chapter, they run autox es in parking lots and you only run in your class against the clock - fun and not too expensive (gas, extra tire and brake wear) usually just have to volunteer to help run events. Sometimes you can get access to used parts from other enthusiasts and some help upgrading your car - in addition to increased driving skill.

I'm not looking to make it sound any sort of way I hate when people go for sound rather then actually power I'm going to actually build this car to its full capabilities just slowly as I have money for it I have a few ideas on what I am going to do was just looking around to see parts the other people would recommend putting on to increase horsepower and in general increase the cars performance

but you CAN make it more fun to throw around corners - suspension and braking upgrades will do that.

 

and shedding mass is good - lighter rims, lightweight crank pulley, lightweight flywheel - all helps it spin-up quicker and accelerate a little faster. take out the rear seat if you never have passengers, leave the spare tire and tools at home if you can always call for help.

 

11lbs mass = ~1 hp

 

4 pounds off rotating mass = ~ 1 hp,

 

it's more fun to drive a slow car fast than a fast car slow.

 

I have a couple of stickers that will add at least 20hp for ya! 

I came across a similar dilemma with my 99obs with an ej22 in it. I added a short throw shifter to it which made the car much more fun to drive and led to performance gains as no more granny shifts. the 99 also go suspension upgrades in white line anti-sway bars with solid end links, and front and rear strut tower braces with Bilstein B8's and the car really came alive even with it's meager HP output. Put Brembo's from a friend's totalled WRX on it also and the little 99OBS is now nothing but fun to drive especially up into the foothills and mountain roads of the Sierras.  Which brings me to the real question: are you wanting to add HP or add performance? Adding performance is specific to what kind of performing you want it to do. If you want to go fast in a straight line then adding HP and performance are the same thing. If you are wanting the car to be able to negotiate something other than a straight line better and in a quicker time, then HP may not be what you are after. Overall performance wise I would start with suspension and braking anyway considering that if you do squeak out a few extra horsepower you are going to want to be able to control it. 

^^^ what he said

 

plus, run stickier tires.