[themyst]

Those plugs look ok to me, normal electrode wear, but nothing visible that would cause a misfire on its own.

When you swapped coil pack from the misfiring cylinder to a different one, did the misfire follow to the swapped cylinder or does it still persist in the same cyl?

if the misfire followed, you know it's a coil pack (since you already ruled out spark plugs). Bad injectors would cause a SES light and the car would shudder and idle rough on cold start. Bad injectors leak into the cylinder slowly causing the aforementioned condition, they are rarely the cause of a WOT misfire.

What's more interesting is that you have no tune. Hope you get it sorted out.

edit - one last fine detail you may want to consider, when you reinstalled the plugs and coils, did you make sure the coils are properly seated in the cylinder and that the plugs are torqued to 17 lbs? It's worth ruling any and all variables out.