Idling problem

There are vacuum leaks and then there are vacuum leaks, unless you went over the car with a fine tooth comb it might still have a vacuum leak. Try a tiny sprtiz of starting fluid along the engine intake and manifold and watch for any corresponding bump in idle speed, indicating a vacuum leak. The PVC elbow is a good place to start. On another note, it might not be vacuum related, could be a throttle position sensor or sensors Ed mentions in the post above.