Hey im new to these forums. I just got an 05 WRX about a week ago and i plan on putting some mods on it. Im not too educated on car mods so i figured joining forums would help. I was thinking exhaust would be cool for sound, even though it only adds about 5 HP. I have about 500-600 dollars to spend by the end of the year and i was curious as to what would give me the best performance without voiding my subaru warranty. Another quick question, does a blow-off valve add any horsepower, or is it just for the sound, and if it does, around how much does it add? Thanks.