My 2001 Pontiac Grand Prix GT is blowing out minimal air through only the vent. The heat and cool air work just fine, you can hear the blower go through all the speeds as well. When I switch the control knob from vent, floor, defrost, ect. The minimal amount of air goes through the just the vents, there is no change in air flow. I have listened for vacuum leaks under the hood but do not hear anything. I have also read conflicting things regarding the blend actuator so I am questioning whether this is the problem. Please let me know what you think.