Hi my name is***** a car technician and I’ll help with your question.
This will almost certainly be a leak on one of the connection on the DPF from when it was replaced. firstly, check your invoice, it should list two gaskets as parts that were fitted, if it doesn't check with the garage to ensure the gaskets were replaced. If they were not changed, that garage should have fitted new and this will be the cause.If they did fit new gaskets, looking visually for leaks is very difficult if not impossible so the best way to cure this is to return to the garage and ask them to re-assembly the joints and inspect to ensure they are sealing. Sealant can be used after the DPF on the joint, but not before so it is very important a new gasket is used on the joint before the DPF.
I hope this answers your question, if you need further assistance, please feel free to reply, otherwise if your happy with my help please remember to "rate" or "accept" my answer, thanks, Ross.
yes there was a new gasket fitted on the joint before the DPF.
Ok, if you have diesel exhaust fumes in the cabin it can only be from the exhaust system so I would advise this is rechecked. If it's more of a warm diesel smell than burnt diesel fumes then I will open up other possibilities?