I just ordered the following parts for my 2000 400ex- e-series s-bend slip on,nerf bars,16 tooth front sprocket,and k&n power kit. will this waken my 400ex up alot or do i need a head pipe

 

well let me start it i guess... i own a 2000 400EX and have a Stroker SX-1 slip on, K&N air filter and Dyno kit... you will not lose much lower area of your power band with the 16 tooth sproket since the pipe, and airfilter will make up for it... you dont need the head pipe, all it does is allow more exhaust to flow out, if your 400 had a big bore kit you would need the head pipe... hope that helps