the header wont intake wont throttle body will but it may not be beneficial unless the aftermarket one is larger than the gsr. Injectors will fpr will thats all I can think of for now. Your exhaust will be too short either use a longer cat or a get a muffler shop to lengthen your exhaust.
Robster

 

actually with an ex or an si you shouldnt need to have any modification done to the exhaust it should bolt up.. mine did..