I at first thought I had a blend door problem but after this weekend I am not so sure. At first I was getting warm air from the vents at idle (outside temp was in the high 70's) then hot air under acceleration. This weekend I was getting cold air from the vents (50's outside) and warm air under acceleration. When I accel, the air does NOT switch to the defrost vents, it stays in the same front vents. Both times the auto air was set to 72, so it was slightly cooler than outside air the first time and much warmer than outside air the second time. Does this sound like a vacuum leak or what? I have not had the time to really mess with it yet, any suggestions on where and what to look for to diagnose and fix this?