Air box Flapper Valve removal

[MississippiDan]

I have a 2017 Yamaha WR250R, I see where some are removing the flapper valve from the air box. I understand it improves throttle response. If I do this will it run lean and require a computer fuel map change ?

[Hey Contevita]

I don't think so. But check it out here: http://wr250r.com/articles/airbox-flapper-mod

[Reserector]

Sounds like they went to a lot of effort to design the flapper. I wonder what, exactly, it does. The article in the link says it helps meet emission standards, but I don't see how.