I believe that you would run a colder plug In a high nitro engine. I also believe they run a colder plug in high RPM set ups. You need to go hotter as the nitro level is dropped or you are running a lower RPM engine. 4 stroke plugs generally are the hottest. If the plugs you are using work fine with your engine/fuel combination then by all means continue to do so. I personally have had good luck with Fox plugs. I like them best so far. OS plugs also have a sterling reputation. I have a few to try some day.

Mark Shuman