Welcome to the club, Simon. I think all the 2.7 diesel engines on the S Type do have a DPF fitted irrespective of the exhaust end bits. I do know that you can buy a DPF for a 2005 S Type for £455. If the DPF is removed it is an automatic MOT failure, although, as it is a visual inspection, some owners have had the DPF removed and the filter casing rewelded and replaced. But, the main thing about the S Type is that it is a great car to drive and looks like a jaguar ought to. Regards, Peter.