I have 1989 f150 with idle surging issue. Currently have codes 41, 32, 34 and 35. All the 30 series codes are for egr pressure differential and 41 is for O2 system. This is not the original engine in the truck this is a 5.0 out of another donor vehicle. Not sure what year. I am looking for guidance on further troubleshooting before i start throwing parts at it. Any help would be greatly appreciated.