2.3 duratec into 3.0 cab

[mattman2479]

hey guys im new and this is my first post but my girlfriend had a 2004 mazda and she totaled it and i bought a 2000 cab and put on the frame the cab was 3.0 and the 2004 was 2.3 duratec the engine harness plugged in the cab but truck has bad idle but i changed the computer but i wonder if i change the harness that goes into cab maybe it would run better