MC Mondeo. Diesel fumes

[FrancisW]

Hi all, just lately car has been getting fumey, especially if sitting, idling and coming to a stop after a Highway run. No smoke. No loss of power, idle a bit rough at times.
I have had vehicle serviced, new filters, including cabin filter. Also had a forced regen.
Exhaust is ok according to mechanic.
Where else do I look.
Could it be injector seals. Cheers