1 plug SHOULD give a misfire on 1 cylinder....random cylinder USUALLY means more then 2. I'd say could even be a 02, but then you should have a bank 1 or 2 rich/lean issue.

Throw a set of cheap plugs in it and see if it goes away... i haven't met anyone actually running e3's yet. i'm a ac-delco platinum/iridium guy myself. 100k miles no problems.