99 Grand Caravan choking and coughing

Took to auto repair several times, could not duplicate, finally able to duplicate and no codes. Nothing, checked plugs, wires, other externals, said that it is not indicative of anything specific.

weird thing is the check engine light never came on, the seatbelt (when you are not wearing it)light never comes on anymore, the door ajar light does not either. Could these things be related?

what it feels like is that it is choking, but per the mechanic it is getting almost TOO much gas he said due to the 'rotten egg' smell that happens when this prob occurs.

any ideas?