Yes, classic symptom of a vacuum leak. The parts do not seal when cold but once the engine warms up the leak goes away.
How did you look for a leak? Most of the tricky ones can only be found using a smoke machine because of the location. One item to check that is missed a lot is the EVAP purge solenoid. If it sticks open even a small amount it acts as a vacuum leak, and because it is internal you will not find it unless you actually test the EVAP system.
Tuesday, January 3rd, 2017 AT 5:49 PM