NGK Racing
Spark Plugs
Got the racing plugs from NGK - dont come cheap and dont last long.
NGK 94237 R0452A-10 General Plug, Semi-Contoured
NGK 94237 R0452A-10 General Plug, Semi-Contoured
In principle, it occupies more space in the combustion chamber hence more compression and slightly more power. Throttle response can be felt if you are sensitive, but not significant.