Earlier quoted context omitted.
There are three main emissions control systems in diesels, the Exhaust Gas Recirculation (EGR), Diesel Particulate Filter (DPF) and Selective Catalytic Reduction (SCR) which uses Diesel Exhaust Fluid (DEF). Any or all can be "deleted" and is a crime to do so. All 3 systems add complexity and potentially reduce performance which is why those who don't care about emissions like to get rid of them. Before DEF NOx regula…
Of course, but mostly it's just recirculation that causes costly engine rebuilds. If it wasn't so expensive no one would delete. Most regulations target emissions at point of sale but don't give a toss if such systems are practical or maintainable. It's sometimes better for the environment to have more emissions but not so much waste from having to buy a new thing more frequently.
That said, many people would prefer the money in their bank account. And if I had decided to sell it rather than fix, no doubt it would have gone to someone looking to delete the DPF.