1995 SL500 Warm Starting Issues.
 

I have a friend that just purchased a SL500.

When cold starting the car runs very well. He will drive 5 or 6 miles, turn the engine off and when he tries to restart the car will crank and eventually fire up but it sounds like only half of the cylinders are firing. He also detects what appears to be a smell of unburnt, raw egg smell when the car runs badly.

Any ideas?.

Thanks much.