I have a 31' IMP with twin 454s. One one runs great the other one backfires through the carb at about 3,200 rpms. I have replaced the carbs and jetted the new ones. I have grounded the distributor and the ignition module. I do not think there is any problem with engine itself. The distributor sensor is rusted could that have any problems?? I'm getting about 3 to 4 psi of fuel pressure. is that enough???

thanks

I once had a keeper come out of a hydraulic lifter and it would not allow the valve to close at higher rpms so it would backfire

check your voltage, also could be a coil going bad.. swap coils and see if the trouble follows.. could do the same with the modules