I have a question about the stock plug, it came with one of those special racing NGK's. This is the same plug as the RM's but it's a #9 not a #8 R-16918B-9 is stock. On kawasaki.com partsdiagram it lists an optional plug R7376 in 8-10 heat ranges. Anyone know the difference? '03's has B9EIX's why the change from this plug?