2005 Pontiac Grand Prix

Heater problem
2005 Pontiac Grand Prix 6 cyl Front Wheel Drive Automatic 75000 miles

I am having an issue with my heater in my 05 Grand Prix. About 8 months ago while starting it, I had smoke coming up from the cowl and into the car on the passenger side. I parked the car till now an am trying to fix the issue. I have replaced the heater relay next to the blower motor and have also replaced the blower but still no heat. I had the switch replaced about 2 years ago. Any advise as to where to look next?
October 30, 2010.

Seems like heater core may be at fault here. That smoke was most likely coolant being blown from the faulty heater core.

Oct 30, 2010.