I had the same issue. It would idle just fine in the driveway and nearly die while waiting at a light. I also noticed after a run and leaving it idling while I went to open the garage door, it would idle slower and slower until it died. The fix for me was to open up the idle screw a turn. I'm guessing that the under hood air temp was hotter while waiting at a light and after a run so the mixture needed to be richer.
