my 2002 sti prodrive starts ok on auto choke but as it coming off it struggles to run,it has no power an if u let the revs drop it will cut out.as soon as the temp gauge moves everything is fine.well except i raced my mates standard wrx 2002 an we were side by side all the way.this is suposed 2 b 315-320 bhp but im not getting that,engine management light comes on an of telling me coilpack no4 but ive changed this twice an put new plugs in an still the same.when i first got it the metal piece on the throttle body thats held on with 2 cross head screws an has a sensor on it is surposed to rotate inside,mine was jamed an the managment light told me this so i soaked it in oil an now it spins but not very freely but no more light coz of it.anyone had this problem or got any ideas???also ive been offered a wrx throttle body complete with sensors 4 50 quid but im unsure if this is the same as my sti,anyone know??