Smell after hard acceleration

[KenSilver]

I don't do this too often, but when I'm in front at the lights on a section of road which goes straight to a 100/kmh area, and the engine is warmed, I like to put my foot down hard and fast. Takes 20 years off my physical appearance immediately

However, the last couple of times I have got a sulphur smell which stays around for 5 minutes or so. Maybe sulphur is not the right description, but more a stale odour.

Anyone know what it is? Catalytic convertor failure? (Do I have one even?)

Ken Silver
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~1993 SL500, glistening triple black, xenons: http://www.kensilver.com/SL
~1999 SLK 230 Kompressor, silver/black leather, CD, immaculate (my wife's)
~1999 Suzuki Grand Vitara. black & silver
~1991 Daimler, shiny grey/grey leather, best in country!
~ex 350SL, 230E, 280E, MX5 and a lot of other makes not nearly as nice.