I had a similar problem with hard starting, especially when warm. Mine (2003) turned out to be one injector going bad. When it was warm the injector would leak on the return side and the pump couldn't make the pressure it needed to start. I ended up getting the miller 9011 tool and capped one line at a time on the rail and when the truck started right up I knew I had found the bad injector. This method may not work if more than one is bad. I was told that this problem may not show up on a scan since it ran great once started. I would make sure all the high pressure lines are torqued correctly first, it may be possible pressure is bleeding off.