HMF full system gains?

[2001400exrider]

hows the gains with a full system HMF? HUGE differnce from stock? Im hoping its gunna make my ex pull way harder from low end to mid? Lets hear some reviews from HMF owners?!

[cals400ex]

i don't think any pipe on a 400ex makes a huge difference, but noticable. this pipe performs great and i would get one to put on my bike. if you put a cam and piston in your bike, this pipe will do great too.