When you timed the truck did you disco the timing advance. It should be on the passenger firewall. A brown and white wire I believe running into a harness. You have to disco that wire first, which will remove your advance. Then time it to zero, shut off your ignition, and replug that wire. While the wire is unplugged you will register a code. That is the only way to time these trucks exactly. The ignition needs to be off when you disco the wire. Start it, time it, kill it, reconnect. When you reconnect the computer will advance appropriately.