IF your trading catback for catback, find out the diameters of the piping. If the tenzo is like a 3inch pipe, then you know why the dude wants to trade! ITs hard to determine the correct exhaust diameter, when you have to consider your current mods, and correct back-pressure, etc.. But along the lines of Nakayama and Tenzo exhausts, if they are both the same diameter, and both mandrel bent (constant diameter throughout the bends) then doesnt seem like its worth the trade. thats just my opiniono.