I have an 807 executive Automatic and have problems with the hot air butterfly in the air doser falling to bits. A new air doser it would appear that the intercooler butterfly valve is full open and the hot air direct from the turbo is fully closed. Can it be that the vacuum system operating the valves is faulty and the hot air valve is not opening correctly causing too much heat through restricted air flow which the causes the DPF to block completely.the valves. How can I check the vacuum system and where is it located please. Terry XXXXX *****@******.*** Laleham Staines Upon Thames.