Re: What Pipe?
it's not on a 400 ex, but i've got a pro circuit t-4 on my warrior. i don't know about 7 hp, but it helped alot. before taking off in 2nd gear wasn't easy, but it's cake now. they say you don't have to rejet, but i did anyway. it helped too. if you do go to a dealer and buy the jets. i made the mistake of buying a K&N jet kit. 50 bucks for 3 jets and a needle. you can go to a dealer adn buy the jet you need for 5 bucks or so.