You can check easily if it is your ECU by simply pulling the vacuum line, you car should run on base timing. If doing this does make your truck run smoothly, then that's your problem. When you unplug it, your truck will run kind of boggish, but shouldn't die. Based on what you are saying though you have checked alot of things, but I didn't see the pick up coil on your list of replaced items. This would be a place I would definitely check.