1995 Other Ford Models engine light and hunting/idling probl

I have a 2 part question.....my service engine light has been coming on and off for months, recently staying on longer, other problem involves hunting/idling problems between 0 and 1, surging usually in damp or cold weather, when idling at a stop the car actually tries to thrust forward, there was a booster problem with the brakes last year that a friend fixed, all of a sudden I had no brake power or very little and he said the booster was off, had the idle problem at the same time, if the car is idling long enough it will produce smoke from the top of the engine, seems like the car is starving for air and flooding itself. It is a 1995 Mercury Mystique LS, any ideas, have taken it to a few mechanics including Ford Dealership for these 2 problems and was told they don't know what it is..........