iridium for me from now on,saves pissin about.
Irridium plugs were originally intended to extend service intervals as far as i know.
They will foul or whet, exactly the same as copper types but of course will be more expensive in doing so.
They wont cure any mixture or running difficulties and these will remain in the background to trip you up if not addressed.
Just had a bit of this myself, bike would run and then not at all.
Put dirty old plugs back in and perfect running.
Eventually drained the tank and took out about a fivers worth of petrol.
About £1,50 of it was tiny black water droplets!!!
Not seen the like of it before.
AL