Hi All , I have a 1994 E320, It has been running rough randomly even when I am driving.
My wife has been driving it for the last 6 months and has been putting regular gas in it.
When it does start running rough, you can smell a sulferic or burnt fire-cracker smell from the exhaust.
I put some fuel injector cleaner in it, drove it hard on the highway in 3rd gear till it was empty , then i put 91 octane in it and went to do the emissions, the CO and the other one are fine and low, but the NO PPM is very high ( alloawable is 396, it read 3600)
I checked the codes, I got:

code 12
Pin 8
Code 11
I did have a code 5 on the main one, which is EGR valve, but i erased it and still didnt come back, the oxygen sensor ones come back prety fast.

Which both point to the oxygen sensor, but could that cause it to be off that much? I was also thinking the catalytic converter might be bad due to the smell and the use of regular gasoline.
thanks in Advance.

Forgot to mention, I did change the throttle actuator about a year ago, and I did notice a crac in one of the vacuum lines that goes to the tranny, but i dont think a vacuum leak would cause it to fail that much.