It turns out that one of the injectors was stuck wide open creating a ton of soot, plugging the DPF solid. Instead of fixing the injector and cleaning out the DPF, he just drilled holes in the side of the DPF housing until exhaust came out. Ya gotta do what ya gotta do, I suppose. Anyway, I replaced the nozzles and drilled out the catalyst. He don’t need a regen now. I told him he could replace the DPF when he went to sell, but there was no reason to replace it now. That was a couple months ago, and he’s still running fine.