[Ed Wright]

James is correct about the DPF, except that started in mid 2007 for the Duramax. That thing and it's calibration, is a mileage killer. The '06 is the last year to for sure avoid that thing. You can buy an "off-road" exhaust system to get rid of it, but it is illegal as hell. If, however, somebody installs the off-road exhaust system, I (and others) have a nice running calibration for them. Off-road use only, you understand. If you plan to buy a programmer for one, be advised the '07 & later Duramax computers store the checksums and CVN numbers (Just another, redudent checksum) for the last ten calibrations that have been loaded. I have heard guys say "I'll just program it back to stock ten times with my hand-held before I go in for warantee Work". That won't get it, as it only stores one copy of a given set of checksums and CVNs. Only way around it would be to buy a spare computer, and lay the original aside to be installed before taking it back to the dealership. Of course, if you have changed to the off-road exhaust your warantee is gone anyway. Some of these "tuners" and popular hand-helds get carried away with power increases. You can make crazy power increases with a diesel, but it tears stuff up. No reason to expect GM to cover that, but some try to slide that by anyway. All I'll do to them is 60 to 75 hp at the tires and 1 to 1.5 mpg. I'll let the other guys make 200+ more hp and tear things up.