whats teh diffence between them for the 400ex which gives more torque hp and which would be better for a 300ft sand drag race i already got a e-series but im thinkin about gettin the full systems for both so whcih is better for me



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1999 440ex
few mods

 

I had a R4 slip on and now I have a E-series slip on. My 400ex made more horsepower and torque with the R4, its a better pipe in my opinion. I like the E-series thought because you can remove/add disc. The R4 pipe is also lighter, and doesn't hit the ground before the grab bar when you wheelie (like the E-series does). Also the R4 is 2-peice, while the E-series is one peice and the welds crack easily. BTW, the R4 is also LOUDER, but it sounds so awsome!