What mods can i do to my 03' WRX with out having to buy major parts, like is there anything i can just change on engine to get better performance?

catback exhaust, manual boost controler along with a boost guage to make sure you are running a safe amount of boost, ecutek reflashed ecu, better tires.

you can try the 3/16 mod for a while. it may spike abit. i had it for awhile but switched back.
:D

I would try reading here http://www.i-club.com/forums/forumdisplay.php?s=&forumid=60 you can find out alot of stuff just by reading.

Mike