I bought a 95 M3 not too long ago. Passed smog testing no problems here in Texas and seems to run fine. When I run the car a little hard, say up to red line going through a few gears, you can smell a bunch of sulphur odor from the catalytic converter if you have the windows down and come to a stop.
Is this normal or is this an indication of a rich condition? Possible 02 sensors etc.
It's much more noticeable than say my TransAm after running it hard.

Thanks,
Scott

Its possible the honeycomb material inside your cat is burning up, due to a not optimally running engine. Do a tuneup and replace the cat, prefereably with a high flow unit :sun: