exhaust smell
 

I have a 1980 280e euro with manual transmission and when I drive with windows open I can feel the very rich exhaust smell coming from the engine. The fuel mixture and fuel pressure is OK because i had it recently checked and adjusted couple of times. The engine runs really good except for the smell. Mechanic has checked catalytic converter and said it is good. Could faulty valves or something with engine combustion cause that smell.

Thanks