I put this pipe on my Crf450 and it dramatically improved the throttle response, and totally eliminated flameouts/pop stalls.
Yoshimura engineers developed the CRF250R exhaust using experience gained developing the system for the CRF450R exhaust and it works brilliantly. Yoshimura has been the official exhaust supplier to Team Honda Racing for several years now and they have adapted that knowledge to the new CRF250R. Since the CRF250R shares many features and parts with it's big brother, it was an obvious choice which system to provide. All of that experience has helped Yoshimura in making an exhaust that compliments an already great bike. The RS-4 not only increases power and is light, but it also has a lower centralized mass coefficient to provide better handling.