Okay I know we have a upgrade thread, but it is very out dated and with the influx of newer members I decided to take it upon myself to help out....
Below you will find a basic outline for upgrading your WRX/STi. This of course isn't the be all to end all of modding threads and I will add stuff in the future as will other members I'm sure. So here goes....
First and foremost read this thread...
Buying a used WRX/STi ?
Now that we have progressed from buying a car let's jump into what you should be doing
once you have the car.
This is the key to keeping any car road worthy and should include the following;
A) Timing Belt check and replace if needed(check your owners manual for details as to service)
B) Check your fluids; this includes Brake, Clutch, Trans(both auto and manual), power steering, rear diff, coolant and last but not least Oil... More than likely most of these have never been changes in your car so err on the safe side and replace them.
C) Plugs. You should pull them out and check them for fouling, discoloration(lean condition) and damage. Replace them all at once not just one...
D) Suspension parts. Check for cracking, damage and broken parts. Replace both sides at the same time. Make sure you get an alignment as well or at least checked. Also check the CV joints and any type of leaks coming from them. Also wheel bearings.
E) Tires. If you need new tires buy them.
F) Air Filter(pretty self explanatory) Replace if needed.
G) Fuel Filter(this is another one that gets over looked very often so just replace it.)
H) Brakes, yes the nasty of the nasty. Replace as needed.
I) Have your local auto part store run a code reader on your car to look for stored codes(you should have done this before you bought it)
J) Finally keep track of what you did and look at the service records to make sure you keep it up...
On to the next phase Simple Mods.
I will finish this when I get home, power is flickering on and off here at work....until then peace to the east.