strong fume odor, please advise
 

My '82 380 sl has strong fume odor coming fron the front and the rear of the car.

Don't see any black smoke coming from muffler when put the car on netral and press the gas.

When passing the finger over the dashboard or any other part of the vehicle i get black dust.


Please advise what could be the problem, the car runs great.

I just replace the catalytic converter but not the O2 sensor.

One more question, what is the difference on the these catalytic converters: Original $3.100
aftermarket $422 and the one i installed from a local muffler shop $200?