I added the old school afc to my car after I already had the intake,headers, exhaust, pulley and Ecu. and I haven't had a chance to tune on the dyno yet but contrary to what some people say you do notice some difference with the headers, not like NOS difference but it is there. I would get the ECU next or headers. the afc wires right into the ECU harness and correct me if I'm wrong but you will need to retune the afc if you get the ecu later. but thats just my 2 cents and thats about what its worth