I owned a wr 400f 99 model from the first day and I changed to yz timing ,i sold the bike and was looking for a two stroke but no way i am 4 stroker,now here is the comparison when exiting the curves with yz timing the bike didnt spinned that much but damn in technical stuff it did stalled a lot i really hated that,thats why i sold the bike . Now heres the other story i bought a wr 400f 98 model with wr timing damn man i should of never put my other bike to yz timing i love wr timing it never stalls in technical terrain but the only thing you all should be carefull is exiting curves at high speed it overspins so much maybee its because of the torque down low and has power no way im not going back to yz mode ever!!! thats why i posted this topic cause racing with my other friends and trying to catch my little brother i slammed a curve and the bike fanned me so be careful hopefully its just a little crack in my left hand little finger . be honest with yourself are you enduro or motocrosser decide and then prepare your bike dont fool yourself preparing a bike that wont work in what you are going to be doing 80%. just my opinion.