22 crf250r dyno chart

Hello as you can see by this dyno chart the crf seems to have lost alot up top. My question is, is this because of the single exhaust now /mapping or maybe smaller port if anyone has modified the bike and got to comparable numbers as the other bikes at 12-14k rpm? Yoshimura exhaust systems dyno is exactly the same up top so you aren't gaining anything up top with that exhaust so im assuming it must be either mapping or porting that's causing it ?? Almost seems like a 2018 yz250f dyno chart