by bran new carb jets you mean like a rebuild kit? im sure you know if you mess with the intake and/or exhaust your going to have to rejet anyways.
i read about that torq header sparkymichigan makes. kinda wierded out about it though. i looked up the function of an expansion pipe and it got pretty exhaustive for me quick. the fmf pipe makes sense to me; its a bigger pipe with a glass pack. i know theres probably a grip of you guys that have them on your bikes now and love em. idk im no mechanic. i just learn as things come along, but it just doesn't make much sense to me why you can simply make one part of the header bigger and have proper back pressure and all that stuff.
i read a few posts, cant remember where, of a couple guys who had a white bros, loved it, then switched to an hmf and loved them more and supposably got more power out of them. idk what jetting they were at or anything. i just read it a while back. sometime in the future im looking at getting an hmf pipe. my buddy has a trx-250ex. not my favorite bike in the world but that thing sounds wicked. real deap and throaty. i can only imagine what a warrior would sound with one
im curious, what gearing do you have that makes you pull away from a 400? id love to compete with my buddys 450. hes allways telling me to get rid of my warrior and get a yfz450 but shes not going anywhere