I have personally owned a 04 wrx with mrt xb kit(TBE, fuel pump and ecutek tune) pretty expensive think about 4g but I can not say one bad word about it car performed great and was improved fuel efficiency. as stated in this thread a tune you will need is all about adjusting air fuel mixtures and ignition timing also increasing boost for all your mods to work together, don't buy a cold air intake almost every tuner I have spoken to tells me they are worthless! good exhaust brands mrt, xforce, invidia