I put the NGK Iridium plug in mine. I did'nt notice much of a difference in power, but it does start easier. It was fairly expensive for a sparkplug, but I decided that with only one cylinder I should treat her to the best there is.
The number is DPR8EIX-9, there's a lot of info about sparkplugs on NGK's website and they have a product finder there too.
JakeB