the same thing was happening to me. start it up and it knocks and rattles like a 12V, and no throttle response at all. took it to the dealership they did the new flash and have no problems since the flash. i hope it is cured but only time will tell.
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07 3500 DRW,4*4, 6.7L, 6 speed auto,edge juice with attitude, 4" TBE, EGR delete, aFe mega cannon, 19.5 aluminum wheels, pulls 30' stock trailer around midwest