Idleling or driving? How much is coming out a cloud or just a puff every now and then? Is it constant or intermittent? Only does it when the temp is above 80? When did it start doing this?
Probably running rich. My guess is the IAT (Intake Air Temperature Sensor) is bad. It measures the temperature of the incoming air, and calculates the air density. If it's bad, it might make the car run rich or lean, depending on what resistance it has.
This should tell you if your IAT is bad.
Get a small thermometer. Remove the IAT sensor from the rubber intake hose. Then start the car, and insert the thermometer where the IAT sensor was. This should give you a good idea what the temperature is of the incoming air charge. Then, replace the IAT sensor, start the motor, probe both wires coming off of the IAT sensor. Read Voltage and resistance. Then, remove the IAT again, and read the temperature again with the thermometer.
Duplicating the temp. measurments should give you a good idea of the ACTUAL incoming air temp. It won't be exact, but it will be close enough.
Post back with the measurements you took, and we will go from there. I have a graph, which shows the incoming air charge on one axis vs. voltage output or resistance on the other. Can't remember which, but I think it's resistance. Measure both just in case.
I should be able to tell you if it's bad. If the sensor is absolutely dead, then your SES light should be coming on, or codes will be tripped and reading the trouble codes will reveal them.
Scott