a missing in my truck on 1990 Ford F-350

my truck idles fine but when I go down the road it gets a mis in it I changed the plugs, coil, wires, cap, rotor, cap and plugs and still cant find the problem anyone out their help me out I hope someone has some ideas

Asked by for the 1990 Ford F-350
Are the #7 and #8 cylinder plug wires running side by side? If so separate them in the plug wire retainers.

Try running the KOEO (Key On Engine Off) and KOER (Key On Engine Running) tests and post all the codes (including any historical codes) that are generated.

thank you I will try that tomorrow and get those codes out didn't know I could do that my self