Can anyone tell me if the Duramax disables regen during idle? The only other diesel I have owned was a 1986 ford, and if you let it idle it would cool down. I keep hearing that the new ones you should not let idle for any length of time because of the DPF clogging up. I have always heard that is better to let a diesel idle than to start and stop, but does all of this new emision stuff change this?

The normal* regen will not start while the truck is at idle, but if the regen cycle has started and you come to a stop your idle will bump up from the normal ~750 RPM to ~850 RPM and the regen will continue. If you shut your truck down during a regen, the next time you start driving, once your truck comes up to temperature it will finish the regen.

*Note: Normal regen is initiated by the trucks ECM. A service regen can be manually initiated by the service dept at idle, but the trucks RPM will climb well above the normal idle RPM for this procedure.