So ZZP dp with or without cat with a o2 bung. Or quality cat that needs to be welded in? Or a ZZP and a defouler/o2 extension, to be installed where the ZZP bung is, to make it longer so the rear o2, will not mess up with just the o2 in the zzp bunged dp. So this defouler??? Which I think is a o2 extension? Either way it has to have a defouler/o2 extension with or without cat, so the rear o2 is out of the dp not getting to much of a signal, but just enough to stop the cat diagnostics problem?