If you cant get a hangar 9 plug for your evo try a OS F plug ,which is actually a four stroke plug.It is the same as a hangar 9. We can't get Hangar 9 plugs in Australia so I use the OS F plugs and they work great in my Evo's. I also use these plugs in other engines that require a long reach type plug and have found that transitioning from idle to full revs has improved dramatically. Also as stated earlier by others the nitro content of your fuel is the governing factor to which heat range plug you use. If still in doubt just tell the guys at your lhs what fuel you are using etc and I"m sure they will help you select the right one.Good Luck.