I had a very hard time finding BR9EYA plugs to carry as spares (most auto parts stores don't carry them yet). Talked to my dealer, and he said the only difference between them is the split in the electrode the EYA has. He also felt that the EYA burned just slightly hotter than the ES. Also, EVA plugs can be used (as long as they're BR9). I think that is a plated plug, not sure with what though. Bottom line, as long as it's a BR9, you can use it, regardless of the letters after.