1997 Toyota Celica when engine is cold, engine stalls/won't

Hi. When the engine is cold I trouble getting the engine to idle. It will stall out until I keep the RPM's at 1,000 for about a minute or so.
Once the engine warms a bit, it idles fine-holding 800 RPM's. I replaced the throttle postioning sensor, and that seemed to work for a bit, then resorted back. It was doing it every 2nd or 3rd start(like some was sticking), now it is almost every start.
It is worse, of course, when the temperature outdoors is really cold.
I tried adjusting the throttle sensor, and that seemed to work, but then it reoccurs.
The engine has been tuned, and the the throttle body has been cleaned. I cannot seem to find an answer to this one.
I would really appreciate your advise.
Thank you, Marc Aldrich