2.5block w 2.2 head n/a issue

ok hey guys dont beat me up or nothin but i have a few questions that i think i need to get a few bugs out of my car well i got this car 99 rs awd the guy put a jdm 2.5 bolck and all that w 2.2 heads but is still runnin the 2.2 ecu runs like a champs no problems but the idle thats the only issue the guy told me to get a 2.5 ecu out of a 96-00 forester or legecy whats yall input on this i think if i adjust the idle screw it would be ok since i and barly touch the gas to make it idle

thanks for any input is greatly appreciated


well idle screw didnt help w idle