I have a 3.0rb and I find that the car lets off a gassy egg fart smell, everytime I hit full throttle

Is this normal? Does anybody else still experience these smelly gas emissions long after run-in period?
I thought it may be linked to the petrol perhaps? I always pour +98 octane. I regularly use v-power, ultimate 98, and vortex 98 which are suppose to clean your engine as well....hmmm not too sure on their cleaning properties.
Would be interested to hear others thoughts....