the O2 sensors can cause some ruff idle till they get warmed up. But you saay the transmissoin was 'flushed'? That can be a bad thing I have heard, esspeciaally with high miles. The theory is that with high miles, the clutches are worn and when you flush away the matterial in between the clutches, they will slip. Probley when or as the trany warms up the gaps in the clutches get smaller. That make any sense?