It seems that in Europe, there are companies specializing in removing DPF's from diesel cars and removing all traces of DPF software from the ECU. They report significant increases in fuel economy and performance. The kit consists of a pipe that replaces the DPF and the software. And with the DPF removed, you can use 100% biodiesel as well. I read somewhere on a Chevy Duramax forum that fuel economy dropped from 20mpg to 15 mpg when they put a DPF on the Duramax diesel.

Ecotune - economy tuning and performance tuning for cars and commercial vehicles, ecu remap, custom mapping, economy improvement - Ecotune UK Ltd

The kit is expensive though, but it is cheaper than replacing the DPF when it needs replacement. It claims 5 - 10 mpg improvement, which sounds a little far fetched to me. I don't know, but it sounds interesting to me.