Hum 10-13 hp is really not doable for a pipe and a cam change. Carbed bikes don't give up hp and a 08 YZ450 on a Dyno jet made 49+ hp. Maybe a funny Dyno. well believe what you wish, he stated that we were within a couple hp of the pre reverse flow YZ engines. the current yz engines he gets about 61-62 hp out of with a tune. so one of the main reasons im upgrading to the new YZ is because of that engine and the wide ratio trans.