Does anyone run the CR9E that comes stock on the YZ?? I have read that a colder plug is a must for optimal performance. Why do the WR's come with a CR8E (hotter) versus the colder YZ plug (CR9E)?? Is it just to help with plug fouling? I'm sure the colder plug is more prone to foul but if it is better for performance, I think it might be worth the risk of fouling....Any thoughts? Does it really make much difference?