Putting a 97 moter in a 03 win i can git it to run backfiring and poping campurt say 2oxy sinsur catalyst mon. inc

Hello, What codes are you getting from the PCM when you scan it? Did you use the PCM for the 97, or the PCM for the 03? Also, did you change the engine wiring harness out, or did you stick with the one for the 03? Any missing/additional connections?