i'm about to pick up a '04 rex with 20kmiles on it. i'm not new to forced induction (turbo) it's mainly what i've allways owned and been around. but i am new to the subaru platform, i've done some searching, maybe not much, since it's all cluttered with to much stuff. sorry about starting a new thread but this wrx comes with catbac exhaust and i'm going to do the catless up and hiflow cat dp so it will have 1 cat left on the exhaust. now with this free flowing exhaust. do i need to flash the ecu or whatever you guys do to the engine management? just for exhaust? i'm not experienced with engine management so i was wondering how all these flashes/maps/etc work. or can i get by without doing anything to the ecu if i work on the exhaust system for now?