Bog stock my 2010 E made 33 hp on the dyno. To be honest it felt flat as a fart.
Remove airbox lid, get rid of screwed in plug over exhaust spark arrestor, K and N air filter, much better power , 160 main jet, change of needle. Much better just over 36 hp. Still running rich. Night and day change , much better.
Add Yoshi full system, 38 hp ,all at top end. Noticeably more lively at higher revs. A/F ratio spot on, idles much better.
Totally worth it to me but each to their own