l have a 2003 saab 9-3 SE turbo with an upgraded ECU, Stock air intake and exahust, the upgraded ECU helped a lot from 205 hp to 250 hp!! would a performance air intake increase HP and help in overall performance??....thanks!!!

definitely.more air=more power

Yes u can reduce restriction by installing a better air filter & enlarging intake plenums. But be careful. The run of the mill cold air intake systems will either not have ports for all of ur sensors, or they will locate them poorly causing habitual check engine lights. Also u did not state if ur 9-3 is the sport chassis, (9440), or the early 9-3, (9400) chassis. If u have the sport chassis u also have an SA l pump that must be addressed if u put in a cold air system. If not plumbed properly it will suck water & die causing constant check engine lights. Just one last note. If u do have the sport 9-3 be careful as to how much u try to squeeze out of ur SATURN, yes l said Saturn, engine. GM discontinued it in the Saturn line due to failure problems, & while some were addressed before installation in the Saab line not all where. Just do not overdo it & u will be fine. Good Luck