Removing the DPF and other emissions hardware (EGR) might not be "environmentally friendly" or legal, but it does simplify things and theoretically will reduce the amount of possible engine failure modes down the line.

I think fuel economy would likely improve as well with the removal of EGR & DPF since the intake charge would be cooler (EGR) and there would be fewer flow losses due to having no DPF.

Not to mention the added benefit of having clean intake valves instead of the cruddy mess caused by EGR.