did you figure out what it was yet?

 

I have tried the OFF - ON Code test and nothing. The codes were cleared By Car-X. so back to Square 1. Any Suggestions?

 

This sounds SIMILAR to what I just went through with my truck. 93 318 and when I let the truck come to a stop the rpms would go ultra low making it seem like the engine was missing then die. I replaced the IAC (Idle air control) valve and that kept it from dying, but didnt cure all of the rough idle/low rpms all the way. Come to find out that my muffler was plugged up. It was fairly new, less than 2 years old. I could hear a small exhaust leak from the muffler pushing exhaust back into the Catalytic converter when this happened.

My best suggestion is to open all the windows and turn off the radio. Drive it around a bit and see if you can replicate the problem and pay special attention to smells/sounds that happen at the same time. They may help you clue in on what else is going on.