Guys,
My buddy rides an EX400 '03, it's a nice quad but its lacking in the power dept. What are the most cost effective mods that can be done to put out bigger HP numbers.
He was looking into exhausts and things of that sort, what namebrand do you guys recommend.

 

-pipe
-filter
-high compression piston
-cam

 

my 400EX has a stage 1 hotcam, FMF pipe, air filter, and jets. it is a lot more powerful than a stock 400EX. you could also look into getting these power packages i've seen around. i don't know how good they r, but i know white brothers makes one. www. whitebros.com