I know absolutely nothing about cars, but after doing some research i think you might want to investigate the
Semi-surface-discharge configuration
you can see it here in the bottom right:
http://www.sparkplugs.com/glossaryImage.asp?imgID=471
Edit:
Alternativelly K22PB W20EPB
http://www.denso.com.sg/plug/img_ip19.jpg
from
http://www.denso.com.sg/tpl/pdtlineup_plug_lineup.html
