Our 2000 Suburban began a rough idle when cold, ( below 70') to the point of stalling or almost stalling. We took it to a reputable service center. They found a couple of GM service bulletin's, one was the throttle body cleaning that someone suggested to you, another was a reprograming the computer for hesitation on acceleration, but we still had the rough idle until it warms up,(5 min). Then we had a SERVICE ENGINE SOON light come on & My wife got to reading in owners manual about rough idle,misfiring and stalling; the GM comment says that poor grade gasoline could be the culprit and to try a couple tank fulls of a better grade gasoline,(Chevron was recommended by the reputable sevice center). I was surprised they hadn't come up with this comment straight from the owner's manual when they were searching for bulletins relating to rough idle. Anyway we've just filled up with the first tankfull of Chevron high grade and will let you know how it turns out. P.S. Ours uses a qt. of oil every 1,500- 2,000 miles, there was also a bulletin from GM about that, a restricted PVC valve was their $30 answer to that; we haven't installed it yet.