my riding is enduro/desert no MX.
i did 30hrs on the yoshi and so far 10 on the fmf
the fmf 4.1 rct is a far better pipe its much lighter the yoshi is heavier than the stock! i couldnt believe it when i took it out of the box was put off straight away.
the yoshi is extremely loud without the insert its near enough impossible to ride i know loud is sometimes good but its an anoying loud so hi pitched especially where i ride where your 4th and 5th gear flat out most of the time in the desert.
the fmf you can run without insert (just straight through) which is what i do and its still very quiet really deep and plesant.(i guess thats the rct ressonance chamber technology)
the yoshi because you need to run the insert (to loud without )still has the same flat top end as the stock...i dont care what bullshit dynos out there say you can feel it. power down low is slightly more than stock.
the fmf just screams with over rev so much fun to ride because no insert needed and the power is still strong down low much smoother than the yoshi no jerkyiness.
also "looks" wise the yoshi is way to big and fat for the yz cosmetics it just dosent look right. dont be fooled by the pictures on the yoshi site that pipe looks shorter but they have lengthened it and its not the pipe that you will get.
the fmf just looks right.
i wrote this so you guys dont spent twice like i did i read in some moto mag that the yoshi was the way to go but its not.
both pipes are excellent build real quality i couldnt fault the yoshi the stickers are a bit weak on the fmf but they have some new ones now that are hard to fall off. where as the yoshi ones are much better quality.
some people say you need to run inserts as they perform better i completely disagree i have done it with trial and error with my ass on the seat and no inserts kick ass you dont see moto gp bikes running inserts in there bikes.
in summary the yoshi is not a bad pipe but the fmf is better.
anyway hope this helps
ps both were slip ons.
Edited by throttle violence, October 03, 2012 - 07:39 PM.