97' rough start and short wait to start

[fordfarmboy]

I just bought a 97' Ford f250 7.3l with 250,000 miles on it. When I turn the key on the wait to start light comes on for 3-5 seconds and goes off it will start but starts very rough but I can cycle it 5-6 times and it starts pretty decent I pulled off harness to valve covers and had a few brown pins so i changed all glow plugs and put new valve cover gaskets with harness and new external harness pigtails, and new relay. Still acts the same way on starting. I checked relay have power on main with key off and power on other big terminal with key on. What else do I need to check and can i test any help will be great as I'm getting frustrated.