When all was pulled, did remove the AAC unit and cleaned well. If I pull the plenum, I am hoping to be able to see source of cooloant leak, it acts like a loose clamp to a tube, I don't know yet. But the oscillating higher rev to lower rev I have never heard before. And if there is a air intake leak (from who knows where)...still can't understand the sound of air sound releasing after enginge is turned off coming from (sounds like) middle top of engine.??