ok...explain to me how stuffing 4 cylinders worth of exhaust gas down a single exhaust pipe is so much less restrictive? And don't try and come at me with all that scavenging effect of the collector and Bernoulli and all that hocus pocus because you know damn well few exhaust manufacturers have done the math, and if they have, it really only affects a relatively narrow rpm range, and the results are not repeatably manufacturable for $400 a pipe. Really, I am just bull#$%*ting here. I put 4 into1 on most of my bikes too. My kz1000 has 11 to 1 1075cc kit, andrews cams, ported head and vm29 smoothies and a open Kerker. Wack the throttle and scary things happen very fast. So what if I put the factory 4 into 2 with Mega's supplied to Kawasaki by Jardine back on instead of the Kerkert? Wack the throttle and slightly less scary things happen slightly less fast with quite a bit less noise. Whoopie