rotten egg smell in car & at tailpipe
 

Hi everybody. I have a 2012 Mini Cooper R60S with around 57,000 miles. Lately I have noticed a rotten egg smell inside the car and also at the tailpipe at idle. My first thought is the cat. converter is on the way out. I have also seen posts blaming the gas brand that is used. I use Mobil 93 octane. I haven't followed up with a mechanic yet, just wanted to get some opinions first. I haven't noticed any change in performance.