So I just bought myself a 2006 KX250F and it idles fine but when ever you are NOT cranking on the gas it pops like when your giving half throttle or less, Or even when you let off the throttle after giving it some gas it will pop like crazy! It is just needing to be rejetted or something? And also what's like the best type of exhaust system I can install on the bike? Yoshimura RS-2? Pro Circuit ? FmF?