Agree with all that has been said. The EFI system including fuel management and combination of either separate or integrated ignition/fuel side ECU/ECM both is complicated but yet very reliable. Carb motors are much different as a point of reference. Problem might be related to singular or multiple issue(s), but just changing and removing the EFI system is a mistake IMHO. Probably have a link to the block off,etc, but will await your decision moving forward. Good luck in your decision.