You don't get any air flow thur vents on face of dash on a 2004 GMC Safari?

The problem with air flow Thur vents on face of the dash was fixed by repairing the small hard plastic vacuum hose that runs from the PCV valve on the driver side valve cover to a vacuum splitter near the coolant overflow and washer fluid bottles. It gets brittle due to engine heat and cracks or breaks. Your local parts supplier has a soft rubber vacuum

hose that will slip over the line, be sure to inspect the entire line and replace any of it that

feels brittle. 3 ft. of hose $3.00, and about 1 hour time.