1997 Nissan Altima Rough Idle, Help!?

Just to make sure your head gaskits are not blown I would suggest you pull the oil dipstick out and check to see if there are buddles in it. If so you got a gaskit problem. The reason there is white-Grey smoke coming out is if the head gaskits are not blown there is always water in your engine and its is not evaporating in you converter. Last for your idle problem it can be 3 things. One it could be the idle control. 2. it could be your Map Sensor. or last 3. it could be your thoddle body sensor.