2006 and up have the same setup as the 6.1, an integrated dual coil. As mentioned, the stock setup fires the cylinder the coil is in at the same time firing across on another cylinder's partial exhaust stroke. I put the shorties on and its like the 06 and up - fires both plugs same cylinder. I'm not saying there's any measurable power difference, but you can feel it pull harder than before.
Your question was firing order. Its 18436572.
Actually, his subject was firing order, his actual question is "if booth plugs fire at the same time".