I put in an E3 plug for the rally this weekend and did not have good results. Within an hour of riding my bike was missing and backfiring. By the time I got back to camp the bike would stumble everwhere and refused to idle. I pulled the plug and it was black. My bike was just dyno'd so i know the tune is good. Switched back to a NGK and bike ran like champ for the rest of the weekend.