I have a 2011 polo Tdi, everything with it is fine but every now and then when I drive it begins to shoot out white smoke, followed by a strong smell of diesel. My viewpoint it that this is a sensor related issue as if it was mechanical (seal, head gasket failure) then it would be constant or atleast not as random as it currently is. I replaced the dpf sensor and nothing changed. Also when I had pulled some the pipes seeing to the intercooler I saw no oil residue.