So let's say a friend of mine has a newer Duramax diesel with the garbage emissions they install from the factory now, Diesel Particulate Filter (DPF) being the biggest of the problem. Unfortunately the state he lives in requires smog/emissions checks upon registration renewal every two years. He wants to do the necessary stuff to delete the DPF, tune the truck properly and gain back the 4-5 mpg and the 40+hp/80+ft.lbs of torque the factory has taken from him. Although he understands the emissions features are much more environmental friendly, he can't justify how much more unhealthy his diesel motor runs with the added features in a truck that was by no means cheap, and he wants the truck to run as healthy as possible for many years down the road... Are there any other guys out there that live in smog-requiring states and have done this upgrade to their diesels? If so, what do you guys do come smog time? Any input in greatly appreciated and PMs are welcomed.