there's no need for a dpf downpipe, just cut your existing housing, crush the DPF ceramic, take it out, weld it nicely back together, mount it back where it belongs
and, if i'm not mistaken, there's no need for the ECU/whatever computer software update if you don't mind having a little post-injection cycle once in a while
oh, and fill your DEF tank with diesel instead of adblue....