The service manual says not to gap/re-gap iridium plugs. I suspect that's because there's a risk of scraping off/damaging the iridium coating on the electrodes. They should be pre-gapped. But personally, I'd check the gap and very carefully set it to spec if it wasn't correct - I just did that with similar-to-factory spark plugs that had a larger gap than spec... All I had to do was close the gap a bit, with careful pressure on the grounding electrode...
I'm no expert on spark plugs though. Maybe someone else has the spark plug chops to answer more assuredly...
Found this at 'NGK.com' website (not 'THE' NGK's website, though):
"Should I gap my Iridium Plugs?
The manufacturers say NO.
This is because most people do not know how to properly gap a spark plug, and the center electrodes on the ultra-fine iridium can easily snap if mishandled. There is no warranty for snapped center electrodes. The manufacturers say an iridium spark plug will run so much better than a traditional plug, even if it is not gapped for that motor, that they would prefer you just leave it rather than risk snapping the center electrode.
Personally, we at sparkplugs.com, gap our iridium plugs for our own vehicles (we’re rebels). If you insist on gapping your iridium plug, please refer to Proper Gapping for instruction."
http://www.ngk.com/faqmain.asp
Spark Plugs and Gap
