If it is coming from the exhaust have you tried different fuel? An egg smell usually means there is too much sulphur. It could be the DPF needs to re gen or the cat is not getting hot enough. Are you doing mostly short journeys?
Yes, it happened on my 1.9 recently and I've put it down to fuel;
I try to fill up at the local Shell as it's always about 2-3p per litre than surrounding garages, including other Shells nearby.
About 3 months ago after filling the tank I started to get the same sulpherous smell which lasted about halfway into the next tankfull.
The strangest thing was that I seemed to get about 3mpg more out of the "smelly" tankful than usual.
The smell and the extra mpg have now long gone.
No. Octane rating describes how fast the fuel burns. I mean Premium in the sense of a proper fuel supplier that is aware of measuring the amount of Sulphur in the refined fuel and takes steps to reduce it.