sorry about the mutiples posts of this, my computor is messed up. anyway i have heard that HMF is good but anyone know anything better. it must be a full exhaust though.

 

Very very happy with my FMF PowerBomb header and Powercore 4 muffler! EHS racing airbox lid with Outerwears cover, and ProDesign (ProFlow) adapter and foam air filter.

 

I've got buddies with Yoshimura exhaust. I have to say they sound by far the best of any exhaust I've heard. Deep and loud. Makes me want to wet myself. One of them has the slip on only on an otherwise stock '01 400EX. Still sounds amazing. I would run Yoshi if had the money but, since I don't I've found that a fmf powerbomb with White bros. Eseries sound good but must say the MX-4 sounds better and, it's cheaper. Picked one up from Dennis Kirk on sale for $130 marked down from $300. Add powerbomb and have full system for less than $500.

 

I've got a full white bro's eseries on mine and holy crap does it have a nasty deep and loud sound to it!At the top of the rev you think the case is going to split and little creatures are gonna come crawling out to eat you!MY neibors say it's too loud with the spark arrestor removed but i think they are just too old!

 

I forgot to mention if you go with the white bros FULL system you have to order it for a 450r and jet your 400 up1 jett higher than you think or it will run lean white bros say that pipe is for the 400s with the big bore kits or it's too much header pipe!

 

well, ive always been told that HMF and Yoshi are like 1 and 2 for best exhausts. I have also found that HMF is for more low end gains and yoshi is for top end gains. Depends on where you want the power and how loud you want that thing to be. HMF is louder than Yoshi