1988 F350 efi 460 zf5 4x4

Ok, first thing is first, I have checked codes multiple times and fixed the code 41, 33, and 84 that plagued the motor. No other codes as of late. Full tune up too, but to no avail, it still runs rough at idle, around 400-550 rpms. Forgive me but I am only 18, and don't have the ears for what it is/know what to call it, but in 4th, and 5th mostly, when the engine is warm and you try to even moderately accelerate, the rpms go down about 300-400 from the regular cruising rpms. Letting off from the gas gets the rpms back to cruising and you can very slowly accelerate again. Also makes a strange noises out the exhaust, not sure what to call it. From my own thinking it is probably running way too lean for whatever reason (fuel pressure?) but it also smells super rich. Fuel pressure regulator replaced, no change, multiple fuel filters replaced because of dirty tank too. Both tanks perform the same with the front showing past full, and the rear showing empty. Is it possible it could be the frame mounted fuel pump?

Thanks guys for the help!