I no longer endorse the XP985. I had maybe 16,000km (10,000mi) on these plugs in my 2.5. This engine runs exceptionally well and it start developing a slight miss. Most people wouldn't have noticed but I could tell it was there. Turns out, 3 of the 4 plugs were missing the tiny little iridium ground button off the electrode, essentially opening the gap. Maybe just a bad batch but they looked cheesy right out of the box.
Right now it's running cheap NGK V-powers and doing very well on them.