im not too sure myself...because i got an RAC Inspection on a MY00 WRX and i just received the report and on it it said something bout misfiring;

Further investigation required, Misfiring under acceleration, Misfiring under load, Stalls on acceleration

Thats all i got about misfiring from the report...and about the mods and their names and service history... i cannot get my hands on them right now