classicwrxjap

Hi, new to this forum and can't find any threads to answer my question but if there is any can someone please point me in the dire tion.. I'm looking info about mapping my scooby to suit the full stainless exhaust I've fitted. It's a 1994 Pre Facelift wrx classic, jap import. Some folk told me I need a different ecu to be able to map it, is that right? Any help is appreciated