Sounds like your description is the same. My thought is that the door that controls air flow to different areas is vacumn operated, and that there is a leak, hence the lower volume because the "diverter"door is not all the way open, but I don't know that for sure, that's why I am seeking advice here amongst all these tech gurus! Mybe one of them can give us a place to start on both our cars to seek out the problem.