1988 f250 with efi 460, truck was running fine before I took out the zf5 and put in np435. Now I can’t get it to run smooth and it’s not giving me any codes. So far Iv put new plugs, wires, and fuel pressure regulator. It doesn’t hesitate when I give it fuel but it doesn’t smooth out with higher rpms either. The exhaust is darker and stronger than before the swap. Trying to get ideas before I go replacing more stuff that doesn’t need replaced. iv also checked all my injectors and they are pulsing like they should.

 

Found the problem, timing was too advanced, didn't realize my timing was so off when I realized engine cranked a lot faster with ignition off.