2008 >2010 regen in two different ways. Passive when the truck is being worked hard, such as towing or climbing hills with a big payload, this generates enough heat tl remove contaminents frkm the DPF. If you are driving soccermom style it needs to go into active regen, the rear injectors on each cyclinder bank are timed to dump fuel in longer resulting in raw fuel being dumped in the DPF and burning the soot resulting in billowing clouds of white stinky smoke. Could also be a bad intercooler, that has water intrusion. The new 6.7 have an SCR and DEF to eliminate the raw fuel usage resulting in a much cleaner exhaust. That is why EGR and DPF delete kits are prevelant on pre DEF diesels.
