Hi james this might be a bit late , but does this car have throttle body as on some cars when regen is in operation the ecu will operate the throttle body to regulate the amount of air that is needed to control the the 650 degrees for non fuel additve or 450 degress with fuel additive particulate filter temp.If there is no regulation the filter will overheat apparantly 1000 degrees + . so i would check throttle body & smoke induction for any air leaks. Hope this helps Darren