diesels these days have a few thing that are designed to reduce missions but instead they create a fuel sucking, less reliable platform.
Exhaust has recirculation, egr, send a certain amount of the sooty exhaust back through the intake. Soot is not a good thing for throttle bodies, turbos, valves, cylinders, etc.
Next up is the Diesel Particle Filter, dpf. It's exactly what it's name implies. Sounds good in theory except it gets clogged up like any filter and since it isn't a replacement part really since it contains some super expensive metals, trucks go what is called a regen to burn out all that captured soot. In order to do this raw fuel is sent through the engine, into the exhaust and ignited to burn it out. Again, not good for the cylinders and decreases fuel economy. Emissions per gallon increase but decreases emission per mile... doesn't make logical sense, it govt seldom does.
Finally, Diesel Exhaust Fluid, def, is urea, injected into the exhaust to reduce NOx emissions. Good in theory but is a pain in the ass because it can freeze when tank heaters fail, when towing long distances it runs out at very inconvenient times and is not always readily available. And it stinks.
The tuner on the dash is to make the computer think everything is alright and not set any check engine codes for the removed equipment. I went with the straight 4" stainless exhaust because I miss the throaty sound of my old 7.3 diesel and can always add a muffler if I want it to be quieter.
