I have an 03 wrx. i was hoping for some cheap engine mods with some good gains. i have a price range of around $600. Any ideas?

2005 Subaru WRX For Sales Selling a 2005 Subaru WRX Color: Silver Metallic Mileage: 50XXX Mods: NONE!! Perfect if you want a starter Options: All stock features except it also has the spoiler Condition: Good, Car has been in my family since we bought it from Subaru of Stevens Creek '05...