Here's an update on our problem E320:

After nearly two weeks with the dealership service manager, who could never duplicate our symptoms, I brought the car home and drove it on short trips around town with no obvious problems for nearly a week.

Then, on Friday evening on the way home from the office, the phantom fumes returned during a trip of fewer than two miles. The fumes began to affect me almost as soon as I pulled out of the parking space and the check engine light came on.

Monday morning I took the car directly to the dealership. The codes returned indicated an oxygen sensor malfunction and a problem with the upshift delay switch over valve. The dealership doesn't think these have anything to do with problem with fumes.

So far I've been more impressed with possibilities folks here on the forum have come up with than with the ideas from the dealership.

Does anyone have any other ideas, now that we know what the codes indicate?